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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.