Calculating DOF at distance

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dellydel

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Dale
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Hi guys, I wonder if anyone can help me with something I'm struggling to understand...

If I am wanting to take a picture with a shallow depth of field, at, for argument sake, 20m away, how do I work out how much of the image will be in focus from the front to the back and what aperture to use?

Cheers,

Del
 
Hi, thanks for that!

But how do I work it out when I am out and about?

Cheers,

Del
 
dellydel said:
Hi, thanks for that!

But how do I work it out when I am out and about?

Cheers,

Del
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On that DoFmaster site, you can print out tables, or produce your own custom rotary calculator, or download a phone app :thumbs:
 
Thing I have most problem with dof calculators is working out the distance i'm away from the subject. I'm no good at all at guessing distance lol
 
baz83 said:
Thing I have most problem with dof calculators is working out the distance i'm away from the subject. I'm no good at all at guessing distance lol
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Focus on the subject and the distance is shown on the lens. You could also check the distance of background and foreground objects by switching focus to them.
 
Could you elaborate what exactly are you shooting and why do you need to calculate the DOF? You might be simplty trying to solve an unexisting problem.

Did you know that for distant objects DOF is often so large you don't even need to think about it.

As for lanscapes - simply stop your lens down to F8-F11 and manual focus it to hyperfocal distance (there are smartphone apps that can calculate it for you) - you'll get an almost unlimited DOF
 
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gunnar said:
Could you elaborate what exactly are you shooting and why do you need to calculate the DOF? You might be simplty trying to solve an unexisting problem.

Did you know that for distant objects DOF is often so large you don't even need to think about it.

As for lanscapes - simply stop your lens down to F8-F11 and manual focus it to hyperfocal distance (there are smartphone apps that can calculate it for you) - you'll get an almost unlimited DOF
Click to expand...

Well actually, I haven't got my camera yet, so I can't give you an example of what I am trying to shoot. Just trying to get my head around it all in advance!

Do you know of any good Android apps I can use?

CHeers,

Del
 
The thing with digital cameras is that you can shoot and review staight way at minimal / next to no cost so in your place I'd just go out for the day and shoot away to see what works for you :D
 
Now I know I have said it on here before, but what’s wrong with using the depth-of-field preview button?
Some may say that the viewfinder image goes too dark, so if that’s a problem for you then take a test shot and check in on the camera back, enlarging it if necessary.

Sam-D
 
Sam-D said:
Now I know I have said it on here before, but what’s wrong with using the depth-of-field preview button?
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Because it's effectively useless.

Some may say that the viewfinder image goes too dark, so if that’s a problem for you then take a test shot and check in on the camera back, enlarging it if necessary.

Sam-D
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If you've got a decent quality LCD, that works well :thumbs:
 
gunnar said:
I use AndroDOF and DOF Calculator. They do the same things don't remember why I kept both of them :thinking:
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Right, I have got DOFCalculator and I'm trying to get my head around it.

If for arguments sake I was shooting a landscape with a UWA lens (Sigma 10-20 is what I will be getting with a canon 60D) I would enter the following settings,

Camera - Canon 60D
Focal length - 10mm
Aperture - F11
Subject distance - This is what I don't understand; If I'm shooting a landscape what is my subject distance? I presume it is the closet thing I want to see in focus in the frame? If so say it is a wall approx 2 m away, I enter 2m into DOF Calc

I then get a reading of Hyperfocal distance 0.475m
near focus limit 0.384m and the rest is infinite

So, does that mean that anything at 0.384m and onwards will be in focus?

And finally how do I then set my lens to the Hyperfocal distance of 0.475m?

Sorry if I am being dumb!

Cheers,

Del
 
Sounds about right but I think this sums up nicely how ridiculous hypefocal tables / calculators can be as there's no way on Gods earth that they can be this accurate or that you can focus your lens this accurately. Faced with your example I'd select f8 and set the lens to focus at infinity and everything from under two feet to infinity should be acceptable.

There is another way. Divide the focal length by the aperture and you get the size of the thing that can be captured acceptably in mm. So in your example... 10/11=less than 1mm!!! Good enough maybe. My example... 10/8=1.25mm, which gives you a slightly faster shutter speed and a smidgen less diffraction, if you could see it.

See here...

http://www.northlight-images.co.uk/article_pages/hyperfocal_distance.html

One thing to keep in mind if using hyperfocal technique is that you don't need your DoF to exceed your scene, either front or back, so there's no point in using too small an aperture, small enough is enough.

Of course there's yet another thing to think about...

In the real world we don't see things sharp front to back so why not consider letting the far distance drift out of focus? Sometimes this can give a more natural and realistic look.
 
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woof woof said:
Sounds about right but I think this sums up nicely how ridiculous hypefocal tables / calculators can be as there's no way on Gods earth that they can be this accurate or that you can focus your lens this accurately. Faced with your example I'd select f8 and set the lens to focus at infinity and everything from under two feet to infinity should be acceptable.
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Can you explain why it is not possible to focus the lens accurately? Based on the my senario above where the Hyperfocal distance is calculated at 0.475m, do I not just focus the lens at something that is 0.5m approx away then recompose and take the exposure?

woof woof said:
There is another way. Divide the focal length by the aperture and you get the size of the thing that can be captured acceptably in mm. So in your example... 10/11=less than 1mm!!! Good enough maybe. My example... 10/8=1.25mm, which gives you a slightly faster shutter speed and a smidgen less diffraction, if you could see it.
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I don't quite follow, what do you mean by "the size of the thing that can be captured acceptably in mm"?

woof woof said:
One thing to keep in mind if using hyperfocal technique is that you don't need your DoF to exceed your scene, either front or back, so there's no point in using too small an aperture, small enough is enough.

Of course there's yet another thing to think about...

In the real world we don't see things sharp front to back so why not consider letting the far distance drift out of focus? Sometimes this can give a more natural and realistic look.
Click to expand...

Some valid points I never considered....

Thanks for the advice,

Del
 
No need to focus that accurately to hyperfocal, simply focus on tree or something 1m away and switch the AF off.

Remember this simple rules
1. If you focus at infinity, you get everything sharp from infinity to hyperfocal distance
2. If you focus at hyperfocal distance, you get everything sharp from infinity to half hyperfocal distance
3. If you focus somewhere in between infinity and hyperfocal, you get everything sharp from infinity to somewhere between half-hyperfocal and hyperfocal.

In most cases #3 is more than enough
#1 might not work very well if your lens has badly controlled field curvature
 
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I meant that unless you carry a tape measure you can't possibly focus to the nearest cm which is what you could be tempted to do if guided too closely by DoF tables. And of course, can DoF tables be that accurate? I doubt it.

I probably wasn't too clear on the size of things, what I meant was the size of detal that you want to capture, anyway, the linked article is clearer.

When using my 12-24mm I forget about hyperfocal tables and just select a suitable aperture and focus to infinity or a distance that I think will get the result I want. This saves brain ache and carrying around tables or calulators. Alternatively I do the other thing I mentioned and get the foreground sharp while letting the sharpness drift away into the distance for a more natural look.

DoF tables have their uses but I don't think they are worth obsessing over or that the technique should be used all the time, I think it's nice to do something different now and again.
 
Examples of what I was trying to say :D

These shots were taken with a 50mm lens.

The first is at f1.4 and the second is at f8. The point of focus in each is the word "Faith..." on the blue and white boat. In the first the DoF is a little too shallow to be realistic (but I don't care as this was the look I was going for:D) and in the second the DoF is probably a little too deep to be realistic and maybe f5 might have been a good choice. If I'd listened to the voice of the DoF tables I'd have chosen f16-22 which would have been... madness.

IMG_2412-01.jpg


IMG_2413-01.jpg


Again with a 50mm...

Whole image and 75% (or there abouts...) crop.

IMG_3049-01.jpg


IMG_3049-01-c.jpg


Here I tried to get what I could actually see, I could see detail in the twigs but not really in the houses and industrial distance. Here f8 was just about right, although there is still waaaay more detail in the blue bridge when zoomed in than I could see by eye but that's ok as the whole image looks ok, hyperfocal would have meant f32 (which my lens wouldn't do anyway) and would have lead to an unnatural look, IMVHO.

All food for thought :D
 
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Strappy said:
Focus on the subject and the distance is shown on the lens. You could also check the distance of background and foreground objects by switching focus to them.
Click to expand...

Wow, what a plonker. I must read my instruction manuals....I've never heard about this...:cuckoo::bonk::bonk::rules:

Cheers.
 
Thanks for the tip Gunnar!

And cheers Woof Woof for the detailed response, very much appreciated makes things clearer!

Cheers,

Del
 
Strappy said:
Focus on the subject and the distance is shown on the lens.
Click to expand...
I really dont mind embarrasing myself by admitting... I genuinely did not know that :bang: I really do not see what is under my nose sometimes.
I nearly asked the same question as the OP months ago :D
 
If you're lucky... but many lenses only have rough markings and infinity can be quite close to 3 or 5m so guessing a subjects distance can be very hit and miss, another nail in the coffin of DoF tables and their absurd accuracy :D
 
Oh yeah ... it's on my 70-300mm but neither of my others.
Still, it's given me a guide up to 8m and beyond that i'll have to give a little more thought :D
 
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