[orangepeel]

I've just learned about the Hyperfocal Distance (HFD) "rule" and how it's useful for landscape photographers to keep the whole frame in focus - foreground and background.

In summary the HFD is a measure of the distance the closest an object can be to the camera and remain in focus for a given aperture and zoom when you are focused to infinity. Italics are to make this point as it's important. The HFD ONLY comes into play when you focus to infinity.

With fast telephoto ranges the HFD can be measured in kilometers! So it's less useful there. However with wide lenses and small apertures you can decrease the HFD to mere centimeters.

For example, at 10mm / F11 the HFD is around 16cm. (I'll provide tables later.) This means everything from 16cm to infinity is in focus.

It's like the opposite of bokeh. You can use Bokeh creativly to help isolate "the subject" - good for portraits for example. HFD on the other hand, helps make the picture as a whole "the subject" - useful for landscapes


This is an example picture I took today trying to use the HFD rule.



Note the foreground sand & rocks are as much in focus as the lighthouse on the horizon.


Ok, to actually use the rule, follow these steps: -

Compose as normal and get plenty of foreground interest with an expanse of sky or mountains or whatever the landscape is.
Next set to manual focus and set it to the infinity mark on the lens. That's the one that looks like an 8

That's it

The only thing you have to be aware of is don't get any of your foreground within the HFD distance or it'll appear out of focus. I'm not sure if this distance is from the front of the lens or, more likely, the focus plane (the film/ccd itself).


I've said it's of interest to landscape togs. I've no idea if it has other applications - maybe someone more learned than myself can chime in there.


You can see the tables here (Full stops from 8mm to 20mm range) : -
Hyperfocal Distance Results - opcs - IT Services - http://www.askopcs.com/

Or you can download the calculator and make your own tables. Remember to virus scan this exe. It's fresh out of the oven but best to be safe. Just download and run - no installation required.
http://www.orangepeels.co.uk/tmp/Hyp...Calculator.exe


An interesting point to note is that some old disposable cameras that don't have a focus mechanism are actually set in the factory to focus to infinity. That means that the whole scene is in focus. Odd that we spend all this money on gear then try to emulate the effect of a £10 disposable camera

[Gary Bagshawe]

a very good explanation

[fionaB]

got a question........ where is the infinity mark? cos i cant find it anywhere on any of my lenses.

Fi

[Markulous]

Originally Posted by fionaB

got a question........ where is the infinity mark? cos i cant find it anywhere on any of my lenses.

Sadly, they often don't (or even make that never!) put any focus distance marks on modern lenses, nor aperture guides to show what DOF you'd have. Well, we all use Autofocus don't we? .......... NOT!

In theory, manual focus ring to max - tho' some cameras focus past infinity!

'Tis a good explanation, O-P. Now come up with a table that shows the near focus point if I place the far focus end point on infinity - to give me the max available DOF. Oh, except we wouldn't be able to use it with modern lenses (see above!), so it'd only work on good old manual ones! At least we can adapt our dSLRs to M42...... well, up 'til now, anyway!

[Dabhand16]

Fi - the infinity mark is at the very end of the scale at the furthest end of the range. If you do not have it marked, just go the the furthest point of focus on the lens you have.

Another tweak is from memory, I think the depth of the hyperfocal focus range extends further away/behind the point of focus than in front of it, so the very deep depth of field range as described by OP can be achieved with lenses that are not very wide angle (that usually have greater DoF than normal/telephoto lenses) by bringing the focus point back a little from infinity, thus also bringing the DoF nearer to the camera. The greater Dof behind the focus point will then take care of anything further away. I seem to remember some of my old lenses actually having this marked on a scale on the lens itself, although it was not very accurate, it did give an idea of the DoF at any given apatuere.

OP - if this is in the calculator, my appologies - I can't access the link on my work computer.

[Les Meehan]

Peel

Good explanation but I'm afraid you have only told half the story here.

Golden Rule: NEVER focus your lens on Infinity if you want maximum DoF!!

You are correct when you state that the HFD is found by setting the lens focus to infinity. The steps are:

1. Set lens to manual focus and then to infinity focus (if there is not infinity mark simply rotate lens to focus for the the horizon).

2. Now, look at the DoF scale on the lens (WOT! Your lenses don`t have a DoF scale? Hard Luck! Consult the DoF tables Peel provided.) and check the distance shown for each f/No on the scale. These are the various HFD's at the indicated f/No.

3. Now, this is the point Peel has missed, if you want the maximum DoF for the shot you need to refocus the lens to the distance for the f/No you want to use. E.G Let's say that in step 2 the HFD for f/11 shows 10 metres, you must focus the lens to the 10 metre mark and set f/11 on the camera.

This way the DoF extends forward of the focussed distance and back as far as infinity (the horizon). The rule for normal distance i.e. views is that the DoF will be one-third toward the camera from the focus distance and two-thirds beyond it (the furthest limit of which is infinity).

If you focus the lens on infinity for the shot you are LOSING a large amount of the DoF available, this WILL NOT produce maximum DoF!!

Knowing that DoF can extend one-third forward and two-thirds back from the focussed distance for any given f/No allows you to quite accurately determine how much of a scene/subject is in focus and, importantly, how out of focus other things will be. For example, portrait (head and shoulders) against background. Using this method you can alter how the background focus will be by playing around with the 'position' of the available DoF for the chosen f/No. Let's say f/8 gives us a DoF amount of one metre. If the models eyes are the point of focus we have approx 33cm in front of the model in 'acceptable' focus and approx 66cm behind. So if the background is 66cm behind the model it too will be 'acceptably' sharp. Now, if we want to retain the f/No at f/8 but reduce the focus of the background we have two choices. Move the background further away (not always possible), or, move the point of focus forward! i.e. don't focus on the eyes but focus on the tip of the nose or just in front of the nose. This change in focus point (contrary to the rule of focus on the nearest eye!) will move the 'block' of DoF forward hence putting the background beyond the acceptable rear limit of focus, result background goes softer focus but model remains 'almost' the same!

Remember that the only thing in critical focus is what is on the focus plane, everything else is subject to reduced sharpness determined by its distance from this plane. This is why when talking about DoF we use the term 'acceptable' sharpness. This is when an object in a photo looks 'sharp' to the eye. There are factors such as print enlargement, viewing distance and so on that affect DoF too.

Hope this helps to give a fuller explanation of an interesting topic. If my, rather rushed, notes don't click with you let me know and I'll explain differently.

The main problem, as mentioned by others, is that since autofocus was put into 35mm cameras DoF has become one of those subjects that most people don't know about and cannot actually control properly because the cameras are NAFF. Listen up manufactures, we want our creative tools back please!!

Regards

Les

[orangepeel]

Not sure if we're talking the same thing. With DOF and HFD, they are kind of opposites really. DOF is variable by changing the aperture, HFD is fixed for a given focal length / aperture.

I suppose HFD can be thought of as maximum DOF but HFD rules only apply when focused to infinity. They do not work at all if focused at anything else - or at least that's how I understood it.

"the hyperfocal distance is the distance beyond which all objects are acceptably sharp, for a lens focused at infinity."

p.s. all my Nikon lenses (and Sigmas for that matter) have the infinity mark.

[orangepeel]

Just found out something else.

The COC (Circle of Confusion) value in the tables generation in my app is fixed to the 35mm (film) value (0.03) but it's actually different for digital sensors... Here are some common values...

Four Thirds System 0.015 mm
APS-C 0.018 mm
35 mm 0.029 mm


I'll need to fix the calculator so the tables can use a different COC value.

[Markulous]

Must admit I thought that it was max DOF (but was too lazy to check!) as per:

When the lens is focused on the hyperfocal distance, the depth of field extends from half the hyperfocal distance to infinity.
Photography, Phil Davis, 1972.


The hyperfocal distance is the point of focus where everything from half that distance to infinity falls within the depth of field.
John Shaw's Landscape Photography, John Shaw, 1994.


... the hyperfocal distance setting ... is simply a fancy term that means the distance setting at any aperture that produces the greatest depth of field.
How to Use Your Camera, New York Institute of Photography, 2000.

[fionaB]

ok now all that went "woosh"......... i thought the hyperfocus was as Mark i think says the point where u have to focus your camera to get everything fomr foreground to background in focus......
the bit i dont understand ( well all of it really) and forgive me if im being stoopid.......... if you focus on infinite....... and then focus on the hyperfocal distance, what is the point on focussing at all on infinite as that will change as soon as u focus on something else?/

[Markulous]

Ahh, but for landscape photography where do you focus and how do you know what's in focus? So, it's all really so you know what'll be sharp and what you'll deliberately let go OOF (as in the explanation on portraiture by Les)

[fionaB]

ok ...... i can see what u are saying but i still dont see what good focussing on two different places is going to do if u take the shot focussed one the hyperfocal distance why bother focussing on infinite
me thinks this is on more thing im never gonna get

fi