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A-Z Glossary of Photographic Terms

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| A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z |

A


Auto Backlighting Control:
A metering feature that automatically recognises a subject in back lighting condition and increase the exposure to compensate.

Accessory Shoes: - also often called "Hot Shoes ".
The early flash types were simple metal brackets. To install a flash unit, you just slide the mounting foot of the flash into the accessory shoe. No electrical connection is made between camera and flash - it's just a simple and convenient way to attach the flash unit to the camera. Subsequent accessory shoes have been built as part of the camera and usually reat on top of the camera's pentaprism; others are separate items that you mount on the camera body when you need them. Some like the Nikon early professional camera has special dedicated which was designed around the rewind knob.

Aberration:
Failing in the ability of a lens to produce a true image. There are many forms of aberration and the lens designer can often correct some only by allowing others to remain. Generally, the more expensive the lens, the less its aberrations (More attention to optical quality). While no single lens is called a 'perfect lens'. The "ideal" lens would reproduce a subject in a faithful, clearly defined image on film. Aberrations, which can be divided into six basic faults, affect the ideal performance in an optical system.

a) Spherical aberration. Basically, a beam of light passing through a lens parallel to the optical axis converges to form 3 focused images on the sensor. Spherical aberration is the term for an optical fault caused by the spherical form of a lens that produces different focus points along the axis for central and marginal rays.

b) Curvature of field. This optical defect causes points on an object plane perpendicular to the lens axis to focus on a curved surface rather than a plane.

c) Astigmatism. Rays of light from a single point of an object which is not on the axis of a lens fail to meet in a single focus thus causing the image of a point to be drawn out into two sharp lines, one radial to the optical axis and another perpendicular to this line, in two different planes near the curvature of field.

d) Coma. This optical defect causes the image of an off-axis point of light to appear as a comet-shaped blur of light. Coma, as well as curvature of field and astigmatism, degenerate the image forming ability of the lens at the rims of the picture.

e) Distortion. Even if the first four aberrations were totally eliminated, images could result that still have a distorted appearance. For an example, a rectangle may appear as a barrel or pin cushion-shaped object.

f) Chromatic aberration. This aberration is caused by light rays of different wavelengths coming to focus at different distances from the lens. Blue will focus at the shortest distance and red at the greatest distance. Since the natural rays of light are a mixture of colours, each aberration will give a different value corresponding to each colour thus producing blurred images.

Adjustable Camera:
A camera with manually adjustable settings for distance, lens openings, and shutter speeds. Most modern cameras including many compacts now have these functions.

Adjustable-Focus Lens:
A lens that has adjustable distance settings.

Advanced Photo System:
A standard developed by Kodak and four other System Developing Companies - Canon, Fuji, Minolta and Nikon - based on a new film format and innovativefilm, camera and photofinishing technologies. Generally, APS cameras are more compact in size and weight. There are options in various sizes of print out and it will even provide a thumbnail prints (Contact sheet) for you to select or preview prior to actual printing.

AE(Automatic Exposure)

AE-L(Automatic Exposure Lock):
Auto exposure Lock. Metering feature that used to hold the exposure setting when used in the automatic mode. Used most commonly in situation where off centering composition of the subject is desired and to retain the exposure setting of the subject OR where the level of exposure reading both the subject of interest and the background exposure reading is different e.g. back lighting. Used to hold an automatically controlled shutter speed and/or aperture. Recommended when the photographer wants to control an exposure based on a scene's particular brightness area with Centre Weighted or Spot Metering.

Ambient Light:
The available natural light completely surrounding a subject. Light already existing in an indoor or outdoor setting that is not caused by any illumination supplied by the photographer i.e. not by artificial light source.

Angle of View:
The area of a scene that a lens covers or sees. Angle of view is determined by the focal length of the lens. A wide-angle lens (short-focal-length) includes more of the scene-a wider angle of view-than a normal (normal-focal-length) or telephoto (long-focal-length) lens. It can also be explained as the extent of the view taken in by a lens. It varies with the focal length of the lens. Usually expressed on the diagonal of the image area. Basically, there are three types of angles which can be measured (based on horizontal, vertical and diagonals of the film frame), the lens must be designed to cover the widest angle in the diagonal direction. Thus, the angle of view is the angle between imaginary lines drawn from the opposite ends of the film plane to the second nodal point of the lens. All objects within this angle will be recorded by the lens on the film.

APO:
Apochromatic. Having the ability to bring all colours of the visible spectrum to a common plane of focus, within close tolerances, usually refer to a lens with such superior colour correction. Also refer to "ED", "LD", "SD","UD".

Aperture:
Lens opening. The hole or opening formed by the metal leaf diaphragm inside the lens or the opening in a camera lens through which light passes to expose the film. The size of aperture is either fixed or adjustable. Aperture size is usually calibrated in f- numbers-the larger the number, the smaller the lens opening. Aperture affects depth of field, the smaller the aperture, the greater is the zone of sharpness, the bigger the aperture, the zone of sharpness is reduced. The size of the aperture is indicated by its f-number, i.e., the ratio of the diameter of the opening to the focal length of the lens; a large aperture is indicated by a small numerical f-number.

Aperture Priority:
An exposure mode on an automatic orautofocus camera that lets you set the aperture while the camera sets the shutter speed for proper exposure. If you change the aperture, or the light level changes, the shutter speed changes automatically. Apart from the sport or action arena, aperture priority is the most common & effective automatic preference in photography. It can also explained as automatic exposure system in which the lens aperture is set by the photographer, and the camera sets the shutter speed. Can be used in the stop-down mode with any lens that does not interfere with the metering system.

Aperture ring:
A ring, located on the outside of the lens usually behind the focusing ring, which is linked mechanically to the diaphragm to control the size of the aperture; it is engraved with a set of numbers called f-numbers or f- stops.

Artificial light:
Light from a man-made source, usually restricted to studio photo lamp and domestic lighting. When used to describe film (also known as Type A or Type B) invariably means these types of lighting.

Aspherical lens:
A lens whose curved surface does not conform to the shape of a sphere; lenses are usually ground or moulded with spherical surfaces; because a spherical surface lens has difficulty in correcting distortion in ultra-wide-angle lenses or coma in large-aperture lenses brought about by spherical aberration, an aspherical lens is used.

ASA:
American Standards Association. Group that determining numerical ratings of speed for US made photosensitive products. e.g. films. In 1982, its role and its influence was narrowed down by the establishment of the ISO (International Standards Organisation).

Aspect Ratio:
The ratio of width to height in photographic prints - a traditional 35mm film frame is approximately 36mm wide and 24mm HIGH. This has an aspect ratio of 36:24, which can equally well be expressed as 3:2. Some digital cameras use the same aspect ratio for their digital images. For example most digital SLR (single lens reflex) cameras have a 3:2 aspect ratio. However, video monitors typically use a 4:3 aspect ratio. For example a monitor with a 800x600 display has a 4:3 aspect ratio. With this in mind, most consumer level digital cameras use a 4:3 aspect ratio for their images.

Auto Exposure Bracketing:
Auto Exposure Bracketing performs automatic exposure bracketing with varied shutter speed and/or aperture.

Autofocus (AF) :
System by which the camera lens automatically focuses the image of aselected part of the picture subject.

AF-I & AF-S lenses:
Nikon's series of AF lenses, involves the integration of coreless motors into their super telephoto lenses. This gives these lenses quick, ultra quiet autofocus operations. While the AF-S lenses housing a silent wave motor for even quicker and quiet operations than the AF-I lenses, which was being in the stage of being replaced by the newer series.

Automatic Camera:
A camera with a built-in exposure meter that automatically adjusts the lens opening, shutter speed, or both(program) for proper exposure.

Automatic iris:
Lens diaphragm which is controlled by a mechanism in the camera body coupled to the shutter release. The diaphragm closes to any preset value before the shutter opens and returns to the fully open position when the shutter closes.

AV:
The Aperture value, usually refer toaperture settings.


B

B (Bulb) Setting:
A shutter-speed setting on an adjustable camera that allows for time exposures. When set on B, the shutter will stay open as long as the shutter release button remains depressed. Another similar option is the "T" setting, where it never drains the battery power on automatic camera body.

Background:
The part of the scene that appears behind the principal subject of the picture. The sharpness of the background can be influenced by apertures and shuttle set. In the flash mode, bulb setting usually is set for absorbing more ambience light (background information), so the end result of the exposure won't be pitch dark.

Backlighting:
Light coming from behind the subject, toward the camera lens, so that the subject stands out vividly against the background. Sometimes produces a silhouette effect. Always use something (a hand, a lens hood, a lens shade to avoid the light falls onto the lens - to avoid lens flares).

Barrel Distortion:
Straight lines are bowed in at the edges of the picture frame resembling the sides of a barrel; present in small amounts in some wide-angle or wide-angle-zoom lenses, but uncorrected in fisheye lenses.

Balance:
Placement of colours, light and dark masses, or large and small objects in a picture to create harmony and equilibrium. Description applied to colour films and modern DSLR’s to indicate their ability to produce acceptable colour response in various types of lighting. The films normally available are balanced for daylight (550~6000K photo lamps (3400K) or studio lamps (3200K).

Balanced Fill-Flash:
A type of TTL or ETTL-II auto flash operation which uses the camera's exposure meter to control ambient light exposure settings, integrated with flash exposure control. That is, flash output level is automatically compensated to balance with ambient light, resulting in a better exposure for both subject and background.

Balanced fill-flash operation:
A flash photography technique that balances flash illumination with the scene's ambient light. This automatic operation utilizes the some camera's Automatic Balanced Fill Flash System with TTL, ETTL-II Multi Sensor and a compatible dedicated TTL flashgun.

Bellows:
The folding (accordion) portion in some cameras that connects the lens to the camera body. Also a camera accessory that, when inserted between lens and camera body, extends the lens-to-film distance for close focusing or macro photography. Some retain the automatic functions where some have to stop down the lens for manual exposure reading.

Between-The-Lens Shutter:
A shutter whose blades operate between two elements of the lens. Most medium format cameras like the Hasselblad have one family of lens with shuttle and another without. Most lenses in this family have a smaller maximum aperture than the other family.

Blowup:
An enlargement; a print or view that is made larger than the original.

Bounce Lighting:
Flash or tungsten light bounced off a reflector (such as the ceiling or walls) or attachment that fits on the flash to give the effect of natural or available light. Often used to reduce shadows.

Bracket flash:
Also known as handle mount flash. It comprised of one arm of the L-shaped bracket extends under the camera body and uses the camera's tripod socket to mount the camera on the bracket. The vertical arm of the bracket serves as a handle and mounts a flash unit in an accessory shoe often on top of the handle portion, but there are other methods. Flash mounted in a bracket usually requires a separate electrical cord to make the electrical connection between camera body and flash unit. Useful for reducing Red Eye.

Bracketing:
Taking a series of photographs of the same subject at different exposures to insure the "correct" exposure; useful when shooting in situations where a normal metering reading is difficult to obtain. Some top cameras have provision for automatic bracketing, while manually you can bracket by the use of, say, adjust apertures or shuttle speeds setting or both, manually influent the ISO settings or even adjust the flash output power etc.

Burning-In:
Basically, a darkroom or image editing process that gives additional exposureto part of the image projected on an enlarger easel to make that area of the print darker.

Bulb:
Flashbulbs - A special flashbulb that can be used at certain shutter speeds is called "FP" where the initials stand for Focal Plane. Designed for use with focal-plane shutters these bulbs make a nearly uniform amount of light for a relatively long time. The idea is to turn on the light before the focal-plane shutter starts to open and keep the light on until the shutter is completely closed. Firing delay for flashbulbs is indicated by code letters: "F"- fast; "M"- medium; "MF" - medium fast; "S" – slow


C


Camera Angles:
Various positions of the camera (high, medium, or low; and left, right, or straight on) with respect to the subject, each giving a different viewpoint, perspective or visual effect.

Camera shake:
Movement of camera caused by unsteady hold or support, vibration, etc., leading, particularly at slower shutter speeds, to a blurred image on the film. It is a major cause of un-sharp pictures, especially with long focus lenses.

Candid Pictures:
Un-posed pictures of people, often taken without the subject's knowledge. These usually appear more natural and relaxed than posed pictures.

Capacitor:
Electrical component once more commonly known as a condenser. Stores electrical energy supplied by a power source and can discharge it more rapidly than the source itself. Used in flash equipment providing reliable bulb firing even from weak batteries, and supplying the surge needed for electronic flash tubes.

Cast:
Abnormal colouring of an image produced by incorrect white balance or colour temperature settings are used. Can also be found on prints due to many different types of ink and paper combinations. See colour profiling for more information. Can also be caused by reflection within the subject as from a hat on to the face etc.

CCD:
Electronic sensor used by autofocus cameras, capable of detecting subject contrast.

Chromatic aberration:
A lens aberration producing an overall blurred image; the inability of a lens to bring all wavelengths of light (especially red and blue) into the same plane of focus; usually present in regular large-aperture telephoto and super-telephoto lenses; does not improve by stopping down the lens; correctable through the use of Iow dispersion (ED, LD SD) glass. Basically, this aberration is caused by light rays of different wavelengths coming to focus at different distances from the lens. Blue will focus at the shortest distance and red at the greatest distance. Since the natural rays of light are a mixture of colours, each aberration will give a different value corresponding to each colour thus producing blurred images. Often visible as coloured “halos” in digital pictures.

Close-Up:
A picture taken with the subject close to the camera-usually less than two or three feet away, but it can be as close as a few mm.

Close-Up Lens:
A lens attachment placed in front of a camera lens to permit taking pictures at a closer distance than the camera lens alone will allow.

Correction of Aberrations at Close Distance Focusing (or CRC):
In general, lenses are designed for maximum performance at infinity. Accordingly, when the lens barrel is fully extended to the shortest focusing distance, resolution is reduced. Although this is negligible for ordinary lenses, it becomes increasingly important in lens specially designed for close distance photography. Lens designers adopted a system where mechanism moves certain lens components as a unit automatically correcting for aberrations. This assures high lens performance throughout the focusing range.

Coated Lens:
A lens covered with a very thin layer of transparent material that reduces the amount of light reflected by the surface of the lens. A coated lens is faster(transmits more light) than an uncoated lens.

Colour Balance:
How a camera reproduces the colours of a scene. Colour films are made to be exposed by light of a certain colour quality such as daylight or tungsten. Digital cameras do this by setting the white balance or colour temperature. Colour balance also refers to the reproduction of colours in colour prints, which can be altered during the printing process and are directly affected by colour profiling.

Colour temperature:
Description of the colour of a light-source by comparing it with the colour of light emitted by a (theoretical) perfect radiator at a particular temperature expressed in kelvins (K). Thus "photographic daylight" has a colour temperature of about 5500K. Photographic tungsten lights have colour temperatures of either 3400K or 3200K depending on their construction.

CompactFlash:
Most digital cameras with PC Card interfaces use a storage technology called CompactFlash. Standard supported by the CompactFlash Association.CompactFlash is ATA compatible and will fit into any Type II or Type III slot when used with a passive adapter. Available in many sizes and speeds.

Component:
Part of a compound lens consisting of one element (single lens) or more than one element cemented or otherwise joined together. A lens may therefore be described as 4-element, 3-component when two of the elements are cemented together.

Composition:
The pleasing arrangement of the elements within a scene-the main subject, the foreground and background, and supporting subjects.

Computerised flash:
Electronic flash guns which sense thelight reflected from the subject, and cut off their output when they have received sufficient light for correct exposure. Most units must be used on or close to the camera for direct lighting only. And the camera lens must be set to a specific aperture (or a small range of apertures) determined by the speed of the camera shutter.

Contrast:
The range of difference in the light to dark areas of a image (also called density); the brightness range of a subject or the scene lighting. It may be also explained as tonal difference. A image may be said to be contrasty if it shows fewer, more widely spaced tones than in the original.
Or another way to explain, a difference in visual brilliance between one part of the image and another; without contrast, there would be no such thing as a visible image; a line in a photograph is visible only because it is either darker or lighter in tone than the background; every distinguishable part of the image is the result of a contrast in tonal values.

Continuous Servo AF Focus or AI Servo:
Autofocus term used, the AF sensor detection continues as long as shutter release button is lightly pressed and the reflex mirror is in the viewing position. Useful when the camera-to-subject distance is likely to change. The camera “tracks” the subject keeping it in focus.

Contrasty:
Higher-than-normal contrast including very bright and dark areas. The range of density in a image or print is higher than it was in the original scene.

Coma:
A lens aberration restricted to off axis image points; the inability of a lens to render point sources of light near the edges of the frame as circular; the points of light appear as comet-shaped blurs (hence the name coma) with the tails flaring toward the centre of the image; this aberration is very difficult to eliminate in wide-angle lenses with large maximum apertures; it can be reduced by stopping down the lens.

Continuous Servo:
AF Focus detection continues as long as shutter release button is lightly pressed and the reflex mirror is in the viewing position. Useful when the camera-to subject distance is likely to change.

CPU(Central Processing Unit):
The electronic component that controls an electronic product's functions. Essentially, all automatic cameras have at least a CPU to control various functions of the cameras. Some top models have three to five CPU to handle individual task functions - some handle the exposure, one handle the autofocus and so on. Newer autofocus lenses have built-in CPUs to relay information relating to focal length, distance info, lens type to the camera body for exposure to AF processing.

Cropping:
Printing only part of the image, usuallyfor a more pleasing composition, in medium format. May also refer to the framing of the scene in the viewfinder.

Curvature of Field:
This optical defect causes points on an object plane perpendicular to the lens axis to focus on a curved surface rather than a plane.

D


D-type AF Nikkor lenses (Only apply to Nikon):
AF Nikkor lenses that send Distance Information to some of Nikon's cameras, used for 3D Colour Matrix Metering or 3D Multi Sensor Balanced Fill Flash. Some third party lens manufacturers also supply compatible functions lenses too.

Darkroom:
A light tight area used for processing films and for printing and processing papers; also for loading and unloading film holders and some cameras. For image purist, the cycle of photograph is not complete if the darkroom process is not handled personally. Modern day equivalent is the image editor, (Photoshop, Paint Shop Pro, C1) many of which are available.

Dedicated Flash:
A fully automatic flash that works only with specific cameras. Dedicated flash units automatically set the proper flash sync speed and lens aperture, and electronic sensors within the camera automatically control exposure by regulating the amount of light from the flash. A simple glance can differentiate by identifying the multiple contacts on the hot shoe (the place where the flash is mounted).

Definition:
The clarity of detail in a photograph.

Delayed action:
Mechanism delaying the opening of the shutter for some seconds after the release has been operated. Also known as self-timer.

Depth of Field:
The zone of acceptable sharpness in front of and behind the subject on which the lens is focused; extends approx. one-third in front of and two thirds behind the in-focus subject; dependent on three factors: aperture, focal length, and focused distance; the wider the aperture, the longer the focal length, and the closer the focused distance, the less the depth of field, and vice versa; in comparison to a normal lens, wide-angle lenses have inherently more depth of field at each f-number and telephoto lenses have less.
Since this element is very important, another simpler way to explain is the amount of distance between the nearest and farthest objects that appear in acceptably sharp focus in a photograph. Depth of field depends on the lens opening, the focal length of the lens, and the distance from the lens to the subject or can explain as in simpler term as the zone of sharpest focus in front of, behind, and around the subject on which the lens is focused; Many newer DSLR’s allow DOF to be previewed in the camera - very handy for critical work.

Diaphragm:
An adjustable device inside the lens which is similar to the iris in the human eye; comprised of six or seven overlapping metal blades; continuously adjustable from "wide open" to "stopped down"; controls the amount of light allowed to pass through the lens to reach the sensor or film; also controls the amount of depth of field the photograph will have. Openings are usually calibrated in f-numbers. The more blades used will have a more natural and rounded spots. During viewing and focusing, the diaphragm remains wide open, allowing the maximum amount of light to go to the viewfinder for a bright and easy-to-focus image; at the instant of exposure, it stops down automatically to a particular aperture and then reopens to full aperture immediately afterward.

Diffuse Lighting:
Lighting that is low or moderate in contrast, such as on an overcast day.

Diffusing:
Softening of light of the image by means of reflectors or filters.

Dispersion:
The property of materials which have a refractive index that varies according to the wavelength of light, i.e., bend the rays of some colours more than others; a prism placed in the path of a ray of white light bends the blue and violet rays more than the orange and red, so that it spreads out or "disperses" the colours as a continuous spectrum.

Distortion:
Even if the other possible aberrations were totally eliminated, images could result that still have a distorted appearance. For an example, a rectangle may appear as a barrel or pin cushion-shaped object. A lens aberration which does not affect the sharpness of the image, but alters the shape of objects; the inability of a lens to render straight lines perfectly straight; does not improve by stopping down the lens; there are two types of distortion:

Barrel:
Straight lines are bowed in at the edges of the picture frame resembling the sides of a barrel; present in small amounts in some wide-angle or wide-angle-zoom lenses, but uncorrected in fisheye lenses.

Pincushion:
The opposite of barrel distortion; straight lines are bowed in toward the middle to resemble the sides of a pincushion; present in small amounts in some telephoto and telephoto-zoom lenses.

Double Exposure:
Two pictures taken on one frame of film, or two images merged in during post processing. Some cameras can have double exposure level depressed with multiple exposures and even with a motor drive

E

ED:
Extra Low dispersion - usually refer to glass type. Glass with ED properties indicating special rare earth glass or special formulated glass that limiting or correcting of light rays passing through the lens elements to achieve all spectrum of colours to falls on the same plane of focus - especially the Red and Blue spectrum and is usually more apply to longer focal length lenses where the problem is more serious. Pentax and Olympus use the same name as Nikon. Canon's version is called "L" - with red lining and usually their lenses are white in colour. While Minolta uses APO. Independent lens makers, like Tamron, uses LD, Sigma uses APO, Tokina's version is SD APO; all these trade names are basically performing the same functions. Also please refer to "apodchhromatic" .

Effective aperture:
The diameter of the bundle of light rays striking the first lens element that actually pass through the lens at any given diaphragm setting.

EIS:
Electronic Image Stabiliser, better known and often termed as IS. A feature that minimises effect of camera shake. Originally designed for video cameras, Canon has transferred the technology over to its EF lenses and it can offer the facility to hand hold and capture sharp images at slow shutter speeds.

Electronic flash:
Light source based on electrical discharge across two electrodes in a gas-filled tube. Usually designed to provide light approximating to daylight. It is often regarded as artificial light source in the dark. Electronic flash requires a high voltage, usually obtained from batteries through a voltage-multiplying circuit. It discharges a brief, intense burst of light, usually used where the lighting on the scene is inadequate for picture-taking. They are generally considered to have the same photographic effect as daylight. Most flash will correct the colour temperature back to 5000 kelvin - the daylight colour. You can play around with filters mounting on the flash head for some specific effects or alter the colour if necessary. Modern flash has multiple TTL flash exposure control functions and even extend to autofocus control. Some specialized flash are high speed repeating flash which can use for strobocopic effect, UV-flash for ultra violet light photography etc.

Element:
Single lens used in association with others to form a compound construction.

Enhanced Back-Printing:
An Advanced Photo System feature available in some system cameras that enables users to encode detailed information at the time of picture-taking, such as the date and time of exposure, camera settings, roll title or other custom information for subsequent printing onto the back of their photographs. On modern digital cameras is now embedded into the image and if referred to as EXIF data. Many software packages and utilities can read and extract this information.

Enlargement:
A print that is larger than the original image; also see "blowup".

EV:
Exposure value. Method of quantifying scene brightness. Most of these values apply to metering cells, how high or low e.g. a metering that can handle from EV1-EV21 means a metering system that can measure brightness level from just above the light level of a candle light to a brightly sunlight scene on a beach. Camera metering can handle more weakly on a spot meter than, say, a centre weighted average metering system. EV is commonly used in black & White photographic process. At ISO 100, the combination of a one-second shutter speed and an aperture of F1.4 is defined as EV1. The camera may be used only within the EV range of the exposure meter. For example, the exposure metering ranges from EV0 to EV20 can be used on a camera; means the camera's meter can handle broader range of exposure latitude.

Existing Light:
Available light. Strictly speaking, existing light covers all natural lighting from moonlight to sunshine. For photographic purposes, existing light is the light that is already on the scene or project and includes room lamps, fluorescent lamps, spotlights, neon signs, candles, daylight through windows, outdoor scenes at twilight or in moonlight, and scenes artificially illuminated after dark.

Exposure:
The quantity of light allowed to act on a sensor or photographic material; a product of the intensity (controlled by the lens opening) and the duration (controlled by the shutter speed or enlarging time) of light striking the sensor or film.

Exposure bracketing:
Shooting the same subject at a range of different exposures. Some camera provides Auto Exposure Bracketing/Flash Exposure Bracketing.

Exposure compensation:
Exposure compensation for available light is activated by changing the shutter speed and/or lens aperture. This is done by using AE L AF-L (Auto Exposure/Autofocus Lock) button or exposure compensation button, or by Auto Exposure Bracketing . In flash photography with a dedicated TTL flashgun exposure compensation can also be performed by varying the amount of flash output.

Exposure factor:
A figure by which the exposure indicated for an average subject and/or processing should be multiplied to allow for non-average conditions. Usually applied to filters, occasionally to lighting, processing etc. Not normally used with through-the-lens exposure meters.

Exposure Latitude:
The range of camera exposures from underexposure to overexposure that will produce acceptable pictures.

Exposure Meter:
An instrument with a light-sensitive cell that measures the light reflected from or falling on a subject, used as an aid for selecting the exposure setting. The same as a light meter.

Extension bellows:
Device used to provide the additional separation between lens and sensor required for close-up photography. Consists of extendible bellows and mounting plates at front and rear to fit the lens and camera body respectively.

Extension tubes:
Metal tubes used to obtain the additional separation between lens and sensor for close-up photography. They are fitted with screw thread or bayonet mounts to suit various lens mounts and can allow for very close focusing to a subject.


F

F-number
The numbers on the lens aperture ring and the camera's LCD that indicate the relative size of the lens aperture opening. The f-number series is a geometric progression based on changes in the size of the lens aperture, as it is opened and closed. As the scale rises. each number is multiplied by a factor of 1.4. The standard numbers for Calibration are 1.0,1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 22, 32, etc., and each change results in a doubling or halving of the amount of light transmitted by the lens to the sensor. Basically, calculated from the focal length of the lens divided by the diameter of the bundle of light rays entering the lens and passing through the aperture in the iris diaphragm.

Fill-flash:
A method of flash photography that combines flash illumination and ambient light, but does not attempt to balance these two types of illumination. Also see "balance fill flash".

Fill-In Light
Additional light from a lamp, flash, or reflector; used to soften or fill in the shadows or dark picture areas caused by the brighter main light. Called fill-in flash when electronic flash is used. Also see Balanced Fill-Flash.

Film Speed or ISO.
Indicated by a number such as ISO 100 or ISO 400 etc. The sensitivity of a given film to light. The higher the number, the more sensitive or faster (and more grainer) the film. In digital cameras it increases the sensors sensitivity to light which also increases noise captured in the image. Many advances have been made recently and on latest generation DSLR cameras it is possible to get acceptable results up to and inc ISO 3200. Note: ISO stands for International Standards Organization.

Filter
A coloured piece of glass or other transparent material used over the lens to emphasize, eliminate, or change the colour or density (ND) of the entire scene or certain areas within a scene. Also see "colour temperature". Technically, it explained as a piece of material which restricts the transmission of radiation. Generally coloured to absorb light of certain colours. Can be used over light sources or over the camera lens. Camera lens filters are usually glass either dyed or sandwiching a piece of gelatin in a screw-in filter holder. Electronic filters can be applied using image editing software during post processing.

Finder
Also known as viewfinder and projected frame. A viewing device on a camera to show the subject area that will be recorded on the film.

Fisheye lens.
Ultra-wide angle lens giving 180 angle of view. Basically produces a circular image on 35 mm, 5-9 mm lenses showing whole image, 15-17 mm lenses giving a rectangular image fitting just inside the circle, thus representing 180 across the diagonal.

Fixed-Focus
Describes a non-adjustable camera lens, set for a fixed subject distance.

Fixed-Focus Lens
A lens that has been focused in a fixed position by the manufacturer. The user does not have to adjust the focus of this lens.

FL
Florite. A low dispersion mineral used as a substitute for glass in some highly corrected long focal length lenses. Canon uses most of these properties on its EF-L series long telephoto lenses. Also refer to "ED".

Flash
The artificial light source in the dark. Electronic flash requires a high voltage, usually obtained from batteries through a voltage-multiplying circuit. It has a brief, intense burst of light, usually used where the lighting on the scene is inadequate for picture-taking. They are generally considered to have the same photographic effect as daylight. Most flash will correct the colour temperature back to 5000 kelvin - the daylight colour. You can play around with filters mounting on the flash head for some specific effects or alter the colour if necessary. Modern flash has multiple TTL or ETTL-II flash exposure control functions and even extend to autofocus control. Some specialized flash are high speed repeating flash which can use for strobocopic effect, UV-flash for ultra violet light photography etc.

Flash Bracket
Often called handle mount flash. It comprised of one arm of the L-shaped bracket extends under the camera body and uses the camera's tripod socket to mount the camera on the bracket. The vertical arm of the bracket serves as a handle and mounts a flash unit in an accessory shoe often on top of the handle portion, but there are other methods. Flash mounted in a bracket usually requires a separate electrical cord to make the electrical connection between camera body and flash unit.

Flashbulb.
Light source based on ignition of combustible metal wire in a gas filled transparent envelope. Popular sizes are usually blue-coated to give light approximating to daylight. Flash bulbs come in various sizes and types. All work by burning metal' foil in an oxygen 'atmosphere within the glass bulb. Because the light is caused by combustion inside the glass envelope, light intensity increases from zero as combustion begins. It reaches a peak value and then falls off as combustion ends. The flash unit is fired or triggered by the shutter mechanism in the camera. For some flashbulb types in some cameras, the shutter mechanism fires the flash and then waits for a specified time delay before it actually opens the shutter. This delay is to allow the flash bulb to get up to full brightness. See more on FP (focal plane bulb) section.

Flash Exposure Bracketing:
Enables a photographer to automatically bracket exposures at varied flash output levels, in TTL auto flash shooting, without changing the shutter speed and/or aperture; this is a one of the top flash feature that can only be found on some higher ranked cameras.

Flash synchronization:
Timing of the flash coincides with release of the camera's shutter. There are two types of synchronization: Front-Curtain Sync (first curtain), which fires the flash at the start of the exposure, and Rear-Curtain Sync(second curtain), which fires the flash at the end of the exposure. Also see "Rear-Curtain Sync", "Front-Curtain Sync", "X setting".

Flash sync speed:
Exposure time with a focal-plane shutter is measured from the instant the first curtain is released, to begin its travel across the frame, until the instant the second curtain is released, to begin its travel across the frame. When the first curtain reaches the end of its travel, the film frame is uncovered as far as the first curtain is concerned, so it closes the electrical contacts for X sync and fires the flash instantly. Shutter speed at which the entire frame is exposed when the flash is fired in flash shooting. Most modern camera with vertical travel shutter curtain have faster flash sync speed like 1/200 sec. or slower.

Flash output level compensation:
Also known as FEC or flash exposure compensation. A control used to adjust a TTL auto flash operation, enabling an increase or decrease of flash output to lighten or darken the flash effect.

Flash shooting distance range:
The distance range over which a flash can effectively provide light. Flash shooting distance range is controlled by the amount of flash output available. Each automatic flashgun’s flash output varies from maximum duration to minimum duration Close-up subjects will require lower (to minimum) output while more distant subjects will require more light up to the maximum output. The flash shooting distance range varies with the aperture, ISO speed, etc. Also see Guide Number.

Flash Memory Card
A storage medium that uses by most digital cameras. It resembles film in conventional photography. Many different capacities and speeds are available.

Flare
An overall decrease in contrast caused by light being reflected off, instead of transmitted through, a lens surface; controllable through the use of multilayer coating of individual lens elements in a lens; aggravated by unclean lens surfaces on front and rear lens elements or filters.

Flat
Too low in contrast. The range in density in a negative or print is too short or in some cases, reflecting the low resolution produced by a low quality lens.

Flat Lighting
Lighting that produces very little contrast or modeling on the subject plus a minimum of shadows.

Flexible Program:
Flexible Program function temporarily shifts an automatically selected shutter speed/aperture combination while maintaining correct exposure. That is, a desired shutter speed or aperture can be selected in Programmed Auto exposure mode.

F-Number
A number that indicates the size of the lens opening on an adjustable camera. The common f-numbers are f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16, and f/22. The larger the f-number, the smaller the lens opening. In this series, f/1.4 is the largest lens opening and f/22 is the smallest. Also called f-stops, they work in conjunction with shutter speeds to indicate exposure settings. Also can be explained as numerical expression of the relative aperture of a lens at its different stops; equal to the focal length divided by the effective aperture of the lens opening and written in various forms, such as f/8, f8, 1: 8, etc.; each f-number is 1.4 times larger than the preceding one; each number indicates a halving or doubling of the amount of light allowed to pass through the lens; the next higher numbered f-number signifies an aperture which lets in exactly one half as much light, and the next lower number, twice as much light, i.e., f/11 lets in half as much light as f/8, while f/5.6 lets in twice as much; all lenses stopped down to the same f-number produce images of equal illumination (apart from differences due to varying reflection losses); therefore, for a given shutter speed, a given f number always corresponds to the same exposure.

F/stop
A fraction which indicates the actual diameter of the aperture: the "f" represents the lens focal length, the slash means "divided by," and the word "stop" is a particular f-number; for example, with a 50mm f/1.4 lens, the actual diameter of its maximum aperture is 50mm divided by 1.4 or 35.7mm; at f/2, the diameter becomes 50mm/2 or 25mm; at f/2.8, the aperture is 50mm/2.8 or 17.9mm across; as the numerical value of the f/stop increases, the aperture decreases in size.

Focal Length
The distance between the film and the optical centre of the lens, when the lens is focused on infinity. The focal length of the lens on most adjustable cameras is marked in millimetres on the lens mount. The distance from the principal point to the focal point. In full frame and 35mm-format cameras, lenses with a focal length of approx. 50mm are called normal or standard lenses. Lenses with a focal length less than approx. 35mm are called wide angle lenses, and lenses with a focal length more than approx. 85mm are called telephoto lenses. Lenses which allow the user to continuously vary the focal length without changing focus are called zoom lenses.

FP (Focal Plane) flash Bulb
A special flashbulb that can be used at certain shutter speeds is called "FP" where the initials stand for Focal Plane. Designed for use with focal-plane shutters these bulbs make a nearly uniform amount of light for a relatively long time. Generally, FP flashbulbs can be used with any shutter speed and any firing delay except "X sync". The FP bulb will extinguish during exposure intervals longer than 1/60 second but enough light will have reached the sensor to make the exposure.

Focus
Adjustment of the distance setting on a lens to define the subject sharply. Generally, the act of adjusting a lens to produce a sharp image. In a camera, this is affected by moving the lens bodily towards or away from the film or by moving the front part of the lens towards or away from the rear part, thus altering its focal length.

Focus Range
The range within which a camera is able to focus on the selected picture subject - 4 feet to infinity - for example. Extension tubes and close up filters can alter this distance.

Focus-Priority for autofocus:
Shutter cannot be released until the subject s in focus. For situations when an in-focus subjects important. Many cameras use Custom Settings so that you can change the priority.

Focus Tracking:
Enables the camera to analyze the speed of the moving subject according to the focus data detected, and to obtain correct focus by anticipating the subject's position and driving the lens to that position at the exact moment of exposure Canon call this function AI tracking or AI servo.

Fogging
Darkening, lightening or discolouring of image by exposure to non image-forming light to which the sensor is sensitive.

Forced Development
(See Push-processing)

Foreground
The area between the camera and the principal subject.

Front-Curtain Sync:
The flash fires an instant after the front curtain (first curtain) of a focal plane shutter has completed its travel across the film plane. This is the way the camera operates with the flash sync mode at Normal Sync. (See "Rear-Curtain Sync" and “Second Curtain Sync”.)

FPS
Frames per second. Used to describe how many frames the camera can handle automatically per second consequently. Also apply to areas like video, animations, movie cameras.

Free working distance
In close-up photography, the distance between the front of the lens and the subject; increases as the focal length increases; important consideration when photographing shy or dangerous subjects or when using supplementary illumination.

Frame
One individual image or a picture on a roll of film. Also can apply to an object that can be utilised (tree branch, arch, etc.) to frame a subject in composition.

Front lighting
Light shining on the side of the subject facing the camera.

Full aperture metering.
TTL metering systems in which the camera simulates the effect of stopping down the lens when the aperture ring is turned, while leaving the diaphragm at full aperture to give full focusing screen brilliance. The meter must be "programmed" with the actual full aperture, and the diaphragm ring setting.


G 


Ghost images and lens flare.
Bright spots of light, often taking the shape of the aperture, which appear in the camera viewfinder or in the final photograph when a lens is pointed at a bright light like the sun; controllable through the use of multilayer coating of the lens elements.

GN (Guide number)
Used to express the power output of the flash unit. It indicates the power of a flash in relation to ISO film speed. Guide numbers are quoted in either meters or feet. Guide numbers are used to calculate the f/stop for correct exposure as follows: Number calculated by multiplying proper flash exposure aperture by the subject distance.

Grain.
Minute metallic silver deposit, forming in quantity the photographic image. The individual grain is never visible, even in an enlargement, but the random nature of their distribution in the emulsion causes over-lapping, or clumping, which can lead to graininess in the final image. Also cross check with below for graininess. In digital terms it is often referred to a noise and is caused by the electronics in the sensor diodes and image processing.

Graininess
The sand-like or granular appearance of an image, negative, print, or slide. Graininess becomes more pronounced with faster film and the degree of enlargement.

Grey card (18% Grey Card).
Tone used as representative of mid-tone of average subject. The standard grey card reflects 18 per cent of the light falling on it. It is often used as a subject for setting a manual white balance.


H


High Contrast
A wide range of density in a image, print or negative.

Highlights
Small, very bright part of image or object. Highlights should generally be pure white, although the term is sometimes used to describe the lightest tones of a picture, which, in that case, may need to contain some detail.

Hot Shoe
The fitting on a camera that holds a small portable flash. It has an electrical contact that aligns with the contact on the flash unit's "foot" and fires the flash when you press the shutter release. This direct flash-to-camera contact eliminates the need for a PC cord. Modern flash demand more than just the main electrical contact and often has more dedicated functions such as TTL control, viewfinder ready light etc.

Handle Mount flash
Also often referred as bracket flash. It comprised of one arm of the L-shaped bracket extends under the camera body and uses the camera's tripod socket to mount the camera on the bracket. The vertical arm of the bracket serves as a handle and mounts a flash unit in an accessory shoe often on top of the handle portion, but there are other methods. Flash mounted in a bracket usually requires a separate electrical cord to make the electrical connection between camera body and flash unit.

Hyperfocal Distance
Distance of the nearest object in a scene that is acceptably sharp when the lens is focused on infinity.


I

Image.
Two-dimensional reproduction of a subject formed by a lens. When formed on a surface, i.e. a ground-glass screen, it is a real image; if in space, i.e. when the screen is removed, it is an aerial image. The image seen through a telescope optical viewfinder, etc. cannot be focused on a surface without the aid of another optical system and is a virtual image.

Incident light.
Light falling on a surface as opposed to the light reflected by it.

Infinity.
Infinite distance. In practice, a distance so great that any object at that distance will be reproduced sharply if the lens is set at its infinity position, i.e. one focal length from the film.

Interchangeable lens.
Lens designed to be readily attached to and detached from a camera.

Inverse Square Law.
This is the law of diminishing luminance that states that light reduces by the inverse of the distance squared. In other words, if the light travels twice as far from the subject, it reduces by its inverse (2x becomes 1/2) and then squared (1/2 x 1/2) = 1/4. So the amount of light falling on a background twice as far away from the camera as the subject being photographed, it will only have a quarter of the light, hence it will be four times as dark.

People often wonder why the subject they lit so beautifully resulted in the background being so dark and this law explains it.

We can extrapolate from this the following:
2x as far = 1/4 the light
3x as far = 1/9 the light
4x as far = 1/16 the light
5x as far = 1/25 the light

Metering is an important consideration so a basic understanding of this principle can be very helpful.

Inverted telephoto lens.
Lens constructed so that the back focus (distance from rear of lens to film) is greater than the focal length of the lens. This construction allows room for mirror movement when short focus lenses are fitted to SLR cameras.

Iris.
Strictly, iris diaphragm. Device consisting of thin overlapping metal leaves pivoting outwards to form a circular opening of variable size to control light transmission through a lens.

ISO Speed
The international standard for representing film sensitivity. The emulsion speed (sensitivity) of the film as determined by the standards of the International Standards Organization. In these standards, both arithmetic (ASA) and logarithmic (DIN) speed values are expressed in a single ISO term. For example, a film with a speed of ISO 100/21° would have a speed of ASA 100 or 21 DIN. The higher the number, the greater the sensitivity, and vice versa. A film speed of ISO 200 is twice as sensitive as ISO 100, and half that of ISO 400 film.



J



K


Kelvin.
A scale use to measure the colour temperature. 5000 K refer to normal daylight.


L

LCD panel ( Liquid Crystal Display.)
Used most commonly on cameras that shows such information as remaining exposures, flash status and aspect ratio selected. Also used for previewing images on the camera.

LD
Low dispersion glass, or UD (ultra low dispersion) or SD (Super Low dispersion), please refer to "ED", basically, refers to optically superior glass - price too! Dispersion sometimes also refer as "colour fringing".

LED
Light Emitting Diode. Light producing transistors used to display dots, numeric and text in the viewfinder, often replaced by LCD display.

Lens
One or more pieces of optical glass or similar material designed to collect and focus rays of light to form a sharp image on the film, paper, or projection screen.

Lens aberration
Optical flaws which are present in small amounts in all photographic lenses; made up of chromatic aberration, spherical aberration, curvature of field, distortion, etc.; a perfect lens would show the image of a point as a point and a straight line as a straight line, but in practice, lenses are never perfect: they reproduce a point as a patch and a straight line as a more or less curved band; most of the trouble is caused by aberrations, inherent in the lens construction; it's the job of the lens designer to control most of the aberrations as much as possible by combining a number of single lenses in such a way that the aberrations of one lens tend to be cancelled out by opposing aberrations in the others.

Lens Hood
A collar or hood at the front of a lens that keeps unwanted light from striking the lens and causing image flare. May be attached or detachable, and should be sized to the particular lens to avoid vignetting.

Lens Speed
The largest lens opening (smallest f-number) at which a lens can be set. A fast lens transmits more light and has a larger opening than a slow lens. Determined by the maximum aperture of the lens in relation to its focal length; the "speed" of a lens is relative: a 400 mm lens with a maximum aperture of f/3.5 is considered extremely fast, while a 28mm f/3.5 lens is thought to be relatively slow.

Light meter
(See Exposure meter)

Lighting ratio.
The ratio of the brightness of light falling on the subject from the main (key) light and other (fill) lights. A ratio of about 3:1 is normal for colour photography, greater ratios may be used for effect in black-and-white work.

Limiting aperture.
The actual size of the aperture formed by the iris diaphragm at any setting. Determines, but usually differs from, the effective aperture.

Long-focus.
Lens of relatively long focal length designed to provide a narrower angle of view than the normal or standard lens, which generally has an angle of view, expressed on the diagonal of the film format, of about 45 degrees The long focus lens thus takes in less of the view in front of it but on an enlarged scale.

Lux
A measurement of the light intensity. One Lux in video means light level of a candle light.


M

Micro lens
A lens for close-up photography; designed to focus continuously from infinity down to a reproduction ratio of 1: 2, or with a matched extension ring or teleconverter down to 1: 1; available in normal or telephoto focal lengths to provide a variety of free working distances. Macro or Makro (Usually for German origin lenses).

Macro photography
The process of taking photographs of small objects with regular photographic lenses at reproduction ratios of 1X or greater; also referred to as "photomacrography. "

Magnification ratio
Commonly referred to compact size sensors in modern DSLR cameras. Also know as crop factor. It affects the range of the lens by effectively “magnifying” the image making zoom lenses seem to have a greater range and reducing the angle of view on wide angle lenses. Most modern DSLR have a 1.6 crop factor.

Manual:
User selects both shutter speed and aperture, following or ignoring the meter's recommendations to achieve the desired exposure.

Manual flash:
Flash output is controlled manually in manual flash mode unlike in auto flash mode, where flash output power varies automatically according to the selected aperture. Some flashguns provide selectable manual outputs (full, 1/2, l/4, 1/8, l/16 etc.), while others provide full manual output only.

Manual iris.
Diaphragm controlled directly by a calibrated ring on the lens barrel.

Matrix Metering system:
An exposure metering system using a multi-segment sensor and computer. With the classic techniques of evaluating for 18% reflectance, factors such as brightness and contrast are primarily used to determine exposure. In addition, it is essential to evaluate each scene's aesthetic factors such as colour to get the best exposure.

Maximum aperture
The widest aperture which the diaphragm is capable of opening up to; it is engraved on the lens in this manner; 1: 1.4.

Mirror lens (Reflex Lens).
Lens in which some (usually two) of the elements are curved mirrors. This construction produces comparatively lightweight short fat long focus lenses. They cannot be fitted with a normal diaphragm.

MTF
Modulation Transfer Function. The way people (who else, the magazines!) uses to measure a lens's ability to hold diminishing details of a subject. Why MTF ? Because, everything is done electronically and eliminating any errors in human judgement or vision and results can be repeatable to counter check earlier tests. Secondly, a precise comprehensive rating is made possible by incorporating huge amount of data into a single reading, lastly it is very fast and permit its use on just out from production lenses.

Modelling.

Representation by lighting of the three-dimensional nature of an original in a two-dimensional reproduction.

Monitor Pre-flash(es):
When performing Automatic Balanced Fill-Flash with TTL Multi Sensor, the Flashgun fires a series of scarcely visible pre-flashes to enable the camera's computer to pre-analyze the scene. The TTL Multi Sensor inside the camera body reads the amount of reflected light, then the camera's microcomputer determines the area of the TTL sensor to be used for flash output control and adjusts the flash output level. The Monitor Pre-flashes are visible but not recognizable

Multilayer coating
The depositing of multiple coats of anti-reflective materials on a lens surface to reduce ghost images and flare produced by internal reflections and insure faithful colour rendition. The number of layers is determined by the type of optical glass and the position of the element in the lens design.



N


ND
Neutral Density. Usually applies on filter, filtration that can effectively reduce the amount of light passes to the film. In some filters, half ND filters can be very effective to lower the contrast, especially the sky to achieve more balance effect. Lens like reflex lenses, where its aperture is fixed, ND filter can be the only way to play around with exposures.

Nicd or NICAD
Nikel Cadmium. Used as the backbone of most rechargeable batteries. Though not so lasting as alkaline, but have a better resistance to cold than alkaline. When the batteries power is drained out, it will turn "flat" right away (advisable to have spare batteries). Most high speed motor drive handles best when using Nicd batteries.

Normal Lens
A lens that makes the image in a photograph appears in perspective similar to that of the original scene (approximately 45°). A normal lens has a shorter focal length and a wider field of view than a telephoto lens, and a longer focal length and narrower field of view than a wide-angle lens. Normal lenses corresponding to that portion of human vision in which we can discern sharp detail; technically defined as a lens whose focal length is approximately equal to the diagonal of the film frame; in 35mm photography, the diagonal measures 43mm, but in practice, lenses with focal lengths from 50mm to 60mm are considered normal.


O


OTF Test (Optical Transfer Functions)
Evaluates lens performance in terms of resolving power, contrast rendition and aberrations. Most believe the test is the only way to determine how good a lens is in the lab

Overexposure
A condition in which too much light reaches the film, producing a dense negative or very bright/light sections of the image.


P

Panning
Moving the camera so that the image of a moving object remains in the same relative position in the viewfinder as you take a picture. The eventual effect creates a strong sense of movement.

Panorama
A broad view, usually scenic.

Parallax
With a lens-shutter camera, parallax is the difference between what the viewfinder sees and what the camera records, especially at close distances. This is caused by the separation between the viewfinder and the picture-taking lens. There is no parallax with single-lens-reflex cameras because when you look through the viewfinder, you are viewing the subject through the picture-taking lens.

PC Cords
The purpose of sync cords is to allow the camera to control the flash, so the flash fires at the correct time. Other common names for electrical cords to connect flash to camera are PC cord, sync cord and synch cord. One type of electrical connector on camera bodies is called a PC socket, whence the name, PC cord. Sync and synch are both intended to be abbreviations of the word synchronization.

PC Terminal/PC socket
Some older flash units may not have a hot shoe on the flash unit and would need cable connection to fire timely. It is a threaded collar surrounding the centre electrical part of the socket. Some flash cords have a connector that makes electrical contact with the centre part of the socket and is held securely in place by a threaded ring which screws into the outer part of the socket on the camera body. It is another alternative way to sync the electronic flash on the camera. Some of the modern autofocus cameras have omitted this feature on the body. It can also be used to activate another flash unit via sync cord in a multiple flash setup. PC sockets and common PC cords fit together by pushing the connector on the cord into the socket on the camera. It remains connected only because of friction.

PC (photographic 2)
Perspective control. Also known as tilt or shift lenses. Lenses that allow for correction of linear distortion resulting from high or low camera angle. Most are with gear or sliding mechanism and most require manual metering.

Perspective
The rendition of apparent space in a flat photograph, i.e., how far the foreground and background appear to be separated from each other; determined by only one factor: the camera-to-subject distance; if objects appear in their normal size relations, the perspective is considered "normal"; if the foreground objects are much larger than the ones in the background, the perspective is considered "exaggerated"; when there is little difference in size between foreground and background, we say the perspective looks "compressed."

Picture angle
The angle of coverage of a lens usually measured across the diagonal of the picture frame; varies with focal length: the longer the focal length, the narrower the picture angle; the shorter the focal length, the wider the picture angle. Telephoto ratio is derived by dividing the distance from the front vertex of a lens to the front vertex by the focal length. The smaller the telephoto ratio, the smaller the total length of the lens.

Pincushion Distortion
The opposite of barrel distortion; straight lines are bowed in toward the middle to resemble the sides of a pincushion; present in small amounts in some telephoto and telephoto-zoom lenses.

Photomicrography
The process of taking photographs of minute objects using a camera and a microscope; not to be confused with "microphotography," the process of making minute photographs of large objects.

Plane.
Level surface. Used in photography chiefly in respect to focal plane, an imaginary level surface perpendicular to the lens axis in which the lens is intended to form an image. When the camera is loaded the focal plane is occupied by the film surface.

Polarising Screen (Filter)
A filter that transmits light travelling in one plane while absorbing light travelling in other planes. When placed on a camera lens or on light sources, it can eliminate undesirable reflections from a subject such as water, glass, or other objects with shiny surfaces. This filter also darkens blue sky.

Polarized light.
Light waves vibrating in one plane only as opposed to the multi-directional vibrations of normal rays. Natural effect produced by some reflecting surfaces, such as glass, water, polished wood, etc., but can also be simulated by placing a special screen in front of the light source. The transmission of polarized light is restrained by using a screen at an angle to the plane of polarization.

Preset iris.
Diaphragm with two setting rings or one ring that can be moved to two positions. One is click-stopped, but does not affect the iris, the other moves freely and alters the aperture. The required aperture is preset on the first ring, and the iris closed down with the second just before exposure.

Post Processing
Developing of the image, from Raw data or in camera converted file formats.. depending on the software used, many elements can be adjusted at this stage including, exposure, brightness, colour, saturation etc.

Program Exposure
An exposure mode on an automatic or autofocus camera that automatically sets both the aperture and the shutter speed for proper exposure.

Programmed Auto:
Camera sets both shutter speed and aperture for correct exposure.

Push Processing
Increasing the development time of a film to increase its effective speed (raising the ISO number for initial exposure ) for low-light situations; forced development.


Q



R

Rangefinder
Instrument for measuring distances from a given point, usually based on slightly separated views of the scene provided by mirrors or prisms. May be built into non-reflex cameras. Single-lens reflexes may have prismatic rangefinders built into their focusing screens.

Rear-Curtain Sync:
Flash fires an instant before the second (rear) curtain of the focal plane shutter begins to move. When slow shutter speeds are used, this feature can create a blur effect from the ambient light, i.e., a flowing- light patterns following a moving subject with subject movement frozen at the end of the light flow. (See "Front-Curtain Sync".) Most mid range and top flight auto camera models have this feature.

Refractive index
A technical term used to describe the effect of a lens in causing light rays to bend; important aspect in lens design.

Reflector
Any device used to reflect light onto a subject to improve balance of exposure (contrast). Another way is to use fill in flash.

Relative aperture.
Numerical expression of effective aperture, also known as f-number. Obtained by dividing focal length by diameter of effective aperture.

Release-Priority:
For autofocus, shutter can be released anytime (i.e., even when subject is not in focus). Helps you avoid missed opportunities when you are not concerned with absolute focusing precision, terms apply primarily for Nikon.

Resolution
The ability of a lens to discern small detail; in photography, the image resolution in the final photograph depends on the resolving power of the sensor and on that of the lens the two are not related, but the effective resolution is a function of both.

Reproduction ratio
Term used in macrophotography to indicate the magnification of a subject; specifically the size of the image recorded divided by the actual size of the subject; for example, if the image is the same size as the subject, the reproduction ratio is written as 1:1 or 1X

Retouching
Altering a image after development by use of dyes or pencils to alter tones of highlights, shadows, and other details, or to remove blemishes. Digitally it is often referred to as post processing.

RGB
The red, green & blue, the black is simulated colour. CMYK is the four primary colours.


S


Saturation
An attribute of perceived colour, or the percentage of hue in a colour. Saturated colours are called vivid, strong, or deep. Desaturated colours are called dull, weak, or washed out.

Scale.
Focusing method consisting of set of marks to indicate distances at which a lens is focused. May be engraved around the lens barrel, on the focusing control or on the camera body.

Screen.
In a camera. the surface upon which the lens projects an image for view finding and, usually, focusing purposes. In DSLR cameras. almost universally a fresnel screen with a fine-ground surface. Often incorporates a micro prism or split-image rangefinder.

Selective Focus
Choosing a lens opening that produces a shallow depth of field. Usually this is used to isolate a subject by causing most other elements in the scene to be blurred.

Self-timer.
Mechanism delaying the opening of the shutter for some seconds after the release has been operated. Also known as delayed action.

Semi-automatic iris.
Diaphragm mechanism which closes down to the taking aperture when the shutter is released, but must be manually re-opened to full aperture.

Sensitivity.
Expression of the cameras sensors response to light. Can be concerned with degree of sensitivity as expressed by film speed or response to light of various colours (spectral sensitivity).

Sharpness
A term used to describe the ability of a lens to render fine detail clearly; dependent on the contrast and resolution of a lens and varies with the f/stop; in general, a lens is sharpest at the middle apertures. Also technically can be explained as clarity of the photographic image in terms of focus and contrast. Largely subjective but can be measured to some extent by assessing adjacency effects, i.e. the abruptness of the change in density between adjoining areas of different tone value.

Shutter
Blades, a curtain, plate, or some other movable cover in a camera that controls the time during which light reaches the film.

Shutter Priority
An exposure mode on an automatic or autofocus camera that lets you select the desired shutter speed; the camera sets the aperture for proper exposure. If you change the shutter speed, or the light level changes, the camera adjusts the aperture automatically.

Side lighting
Light striking the subject from the side relative to the position of the camera; produces shadows and highlights to create modelling on the subject.

Single-Lens-Reflex (SLR) Camera
A type of camera that allows you to see through the camera's lens as you look in the camera's viewfinder. Other camera functions, such as light metering and flash control, also operate through the camera's lens.

Slave Unit
Accessory flash "slave" units are available to fire multiple flash units without multiple electrical connections to the camera. These units sense the light output of the first flash, which is mounted in the camera hot shoe, or cord-connected to the camera. When the light output is sensed, the slave unit triggers a second flash unit that is connected only to the slave. Additional slaves and flash units can be used, if needed.

Slow Sync
A flash technique for using the flash at a slow shutter speed. Flash shooting in dim light or at night at a fast shutter speed often results in a flash-illuminated subject against a dark background. Using a slower shutter speed with the flash brings out the background details in the picture. Use of a slow shutter speed with Rear-Curtain Sync is particularly effective for illustrating the movement of a stream of light. Can be of very creative if put to good use.

Soft Focus
Produced by use of a special lens that creates soft outlines. Filters are more popular than lens as it is more economical and flexible.

Soft Lighting
Lighting that is low or moderate in contrast, such as on an overcast day.

SPD
Silicon Photo Diode. Battery powered light sensitive cells - the most common light reading cells for cameras, external metering devices.

Split-image.
Form of rangefinder image, bisected so that the two halves of the image are aligned only when the correct object distance is set on the instrument or. in the case of a coupled rangefinder, when the lens is correctly focused. SLR cameras may have a prismatic split-image system in their viewing screen. Works on the same principle as a microprism, and is restricted to apertures of f5.6 or greater.

Stopping Down
Changing the lens aperture to a smaller opening; for example, from f/8 to f/11.

Stop-down metering.
TTL metering in which the light is measured at the picture-taking aperture. As the meter just measures the light passing through the lens, there is no need for any lens-camera interconnections.

Studio lamps (3200K).
Tungsten or tungsten halogen lamps designed for studio use. Have a longer life than photo lamps, but a lower specific output and colour temperature.

SQF
Subjective Quality Factor. Essentially a lens rating system.

Supplementary Lens.
Generally a simple positive (converging) lens used in front of the camera lens to enable it to focus at close range. The effect is to provide a lens of shorter focal length without altering the lens-film separation, thus giving the extra extension required for close focusing.

Sync Cords
The purpose of sync cords is to allow the camera to control the flash, so the flash fires at the correct time. Other common names for electrical cords to connect flash to camera are PC cord, sync cord and synch cord. One type of electrical connector on camera bodies is called a PC socket, whence the name, PC cord. Sync and synch are both intended to be abbreviations of the word synchronization.

Sync Delay
All electronic flash units require X sync, but flashbulbs require a time delay between firing the flash and opening the camera shutter. The optimum delay varies among flashbulb types, but you will get much of the flashbulb light through the shutter and onto the film even if delay is not exactly correct. Firing delay for flashbulbs is indicated by code letters:"F"- fast; "M"- medium; "MF" - medium fast; "S" - slow

Sync Socket
Often called "PC terminal" or "PC Socket". Most older manual focus SLR camera bodies have this standard PC sockets which have a threaded collar surrounding the centre electrical part of the socket. Some older flash units may not have a hot shoe on the flash unit and would need cable connection to fire the flash (sync) timely with the shutter. Some flash cords have a connector that makes electrical contact with the centre part of the socket and is held securely in place by a threaded ring which screws into the outer part of the socket on the camera body. It is also use for multiple flash set up (non-TTL or manual) where the secondary flash can be used via a sync cord to fire at the same time.

Sync speed:
Exposure time with a focal-plane shutter is measured from the instant the first curtain is released, to begin its travel across the frame, until the instant the second curtain is released, to begin its travel across the frame. When the first curtain reaches the end of its travel, the film frame is uncovered as far as the first curtain is concerned, so it closes the electrical contacts for X sync and fires the flash instantly. Shutter speed at which the entire fiIm frame is exposed when the flash s fired in flash shooting. Most modern camera with vertical travel shutter curtain have faster flash sync speed like 1/250 sec. or slower, some top camera model like Nikon F5, changeable to 1/300 sec. with the Custom Setting.

Synchronisation.
Concerted action of shutter opening and closing of electrical contacts to fire a flashbulb or electronic flash at the correct moment to make most efficient use of the light output. Roughly speaking, FP or M-synchronisation is constructed to fire flashbulbs just before the shutter is fully open, allowing a build-up time, and X-synchronisation fires electronic flash exactly at the moment the shutter is fully open.


T



T (setting)
Setting that holds the camera shuttle open until the shuttle dial is turned or release is press the second time. This setting differs from "B" (Bulb) that it usually is a stand alone setting and never drains the battery power and thus ideal for really long time exposures.

Telephoto Lens
A lens that makes a subject appear larger on film than does a normal lens at the same camera-to-subject distance. A telephoto lens has a longer focal length and narrower field of view than a normal lens and have a shallower depth of field than wide angle lenses. But it can do isolation of subject and have a longer reach without going near to the subject. Life can be very difficult in sports and wildlife photography. Telephoto lens whose focal length is longer than the diagonal of the film frame.

Through-the-lens (TTL).
Type of exposure meter built into the camera body and reading through the camera lens. May measure either at full aperture or at picture taking aperture. (refer below for more descriptions).

Through-The-Lens Focusing
Viewing a scene to be photographed through the same lens that admits light to the film. Through-the-lens viewing, as in a single-lens-reflex (SLR) camera, while focusing and composing a picture, eliminates parallax.

Through-The-Lens Metering
Meter built into the camera determines exposure for the scene by reading light that passes through the lens during picture-taking. Most SLR cameras have built-in meters which measure light after it has passed through the lens, a feature that enables exposure readings to be taken from the actual image about to be recorded on film, whatever the lens angle of view and regardless of whether a filter is used or not.

TTL auto flash:
The camera's light sensor measures flash illumination, as reflected by the subject on the film and shuts off the flash where measurement indicates a correct exposure. Because the sensor that controls the flash receives light through the lens TTL auto flash can be used for bounce flash photography, fill flash, multiple flash photography, etc. An additional advantage of TTL auto flash is that it enables you to use a wide range of aperture settings, while ensuring correct exposure.

Time Exposure
A comparatively long exposure made in seconds or minutes.

Tone
The degree of lightness or darkness in any given area of a image; also referred to as value. Cold tones (bluish) and warm tones (reddish) refer to the colour of the image in both black-and-white and colour photographs.

Toning
Intensifying or changing the tone of a photographic image after processing..

Tripod
A three-legged supporting stand used to hold the camera steady. Especially useful when using slow shutter speeds and/or telephoto lenses. Another is the monopod, single leg tripod.

T/S
The tilt and shift lens, Canon's version of the PC (perspective control) lens.

Tungsten Light
Light from regular room lamps and ceiling fixtures, not fluorescent. Images produced under this light source can be extremely warm, in fact excessive warmth. Need some colour balance filtration or flash to neutralise that.


U


UD
Ultra Low dispersion lens, pls refer to ED, LD sections.

Ultra-wide angle lens.
Extra-wide angle lens, usually those with an angle of view greater than 90°. For 35 mm cameras the description usually applies to lenses of shorter focal length than about 24 mm.

Underexposure
A condition in which too little light reaches the sensor, producing a dark or a muddy-looking image.

Unipod
Also refer as monopod. A one-legged support used to hold the camera steady. Also see "tripod".

UV
The ultra violet ray. This is beyond the visible spectrum i.e. it is invisible electromagnetic radiation of the sunlight.


V



Variable focus lens.
Lens of which the focal length can be continuously varied between set limits. The lens must be refocused with each change in focal length.

Viewfinder.
Device or system indicating the field of view encompassed by the camera lens. The term is sometimes used as a description of the type of camera that does not use reflex or "straight-through" viewing systems and therefore has to have a separate viewfinder.

Vignetting
Underexposure of image corners produced deliberately by shading or unintentionally by inappropriate equipment, such as unsuitable lens hood or badly designed lens. A common fault of wide-angle lenses, owing to reflection cut-off, etc. of some of the very oblique rays. May be caused in some long-focus lenses by the length of the lens barrel.


W


Wide-Angle Lens
A lens that has a shorter focal length and a wider field of view (includes more subject area) than a normal lens. Also can explained as a lens whose focal length is shorter than the diagonal of the film frame; in 35mm photography, lenses shorter than 50mm; also referred to as a "short" lens.

X



X (setting)
Electronic flash units fire virtually instantaneously and reach full brightness immediately. Therefore no time delay is required. Also refer as X sync. Real time setting that causes the flash to burst in synchronises or instantaneously as the shuttle open up. For older manual camera, the X synch speed usually refers to the maximum speed that the camera can have its shuttle curtain open long enough to synchronise with the flash. In fact, if there is a time delay, the electronic flash may be all over before the shutter gets open. To fire electronic flash with a focal-plane shutter, the switch in the camera is closed at the instant the first curtain of the focal-plane shutter reaches fully open-called X synchronization.

X Sync Terminal
Electronic flash units are available which mount on the hot shoe and are triggered by the electrical contact in the shoe. Other types use sync cord which connects to the sync terminal on the camera. Also referred to PC Terminal section.


Y




Z


Zoom Lens
A lens in which you adjust the focal length over a wide range of focal lengths. Substituting lenses of many focal lengths. Zoom lenses whose focal length is continuously variable over a certain range without a change in focus; its focal length is changed by operating a separate zoom or a combination focusing/zoom ring; difficult type of lens to design and manufacture, very useful for the photographer on a budget or one who likes to travel light.