How to Determine a Lens' Maximum DOF

Nintendoeats

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I recently read an article in which somebody referred to a camera/lens combination not gaining appreciable depth of field below a particular aperture size (11 in this case). I was recently doing some nighttime landscape shots and this information would have been useful information since I probably closed my aperture more than was required. However, I cannot find any reference to how this might be calculated, or possibly am not fully understanding something.

I am also not totally clear on how this relates to Hyperfocal distance. It would seem that hyperfocal distance should change with aperture size, but then wouldn't the maximum useful aperture size change based on distance from the nearest object in the frame? I think I'm missing something here.

Thanks!
 

jaomul

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Google Depth of field calculator
 

PJcam

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Depth of field is something I am learning also, it is very important to know about and know how to increase and decrease the depth of field.

As suggested by jaomul, search Google. But you may also like to check YouTube and search Depth of Field there also, there are some good videos on the subject.
 
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Nintendoeats

Nintendoeats

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I have looked at DOF calculators and they are clearly very useful, but I guess this is more of a theory question. Using a calculator, near DOF can always be increased by stopping down. Is the claim that there is an overall "minimum useful aperture" therefore erroneous (or at least true only for a given nearest object), or is there a practical limit imposed by manufacturing and mathematical tolerances?
 

Ysarex

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I have looked at DOF calculators and they are clearly very useful, but I guess this is more of a theory question. Using a calculator, near DOF can always be increased by stopping down. Is the claim that there is an overall "minimum useful aperture" therefore erroneous (or at least true only for a given nearest object), or is there a practical limit imposed by manufacturing and mathematical tolerances?

DOF will increase continually as the aperture is stopped down. BUT at very small apertures diffraction will become a factor and begin to degrade resolution. There is an infinity limit to DOF. You can't increase DOF beyond infinity and infinity isn't infinite. Infinity changes with focal length but it's a distance beyond which no appreciable DOF is possible with smaller apertures. Hyperfocal distance then is the focus distance for any given focal length and aperture combination where DOF extends from 1/2 the focus distance in front to infinity in the back.

Consider an example: A 23mm lens on a crop sensor body set to f/8. Hyperfocal distance is 11 feet. That puts everything in the photo between basically 5 feet to infinity in focus if the lens is focused at 11 feet. What are the odds you have something closer to the camera than 5 feet that you want in focus along with the far horizon? Do you need then to stop down to f/16? At f/8 a crop sensor camera is not diffraction limited, at f/16 it is.

Joe
 
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Nintendoeats

Nintendoeats

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Thanks, that makes it clearer, particularly in conjunction with the diffraction article. I'm going to have to go over it a few dozen times before I really "understand" it, but thou hath answered my question.
 

Sportrunner

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I posted this video in another thread:

He does a great job of simplifying DOF as much as possible. I am including it here for others that are trying to learn more about DOF.
 

PJcam

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I posted this video in another thread:

He does a great job of simplifying DOF as much as possible. I am including it here for others that are trying to learn more about DOF.

That was one of the videos I watched Sportrunner, I found it very helpful, as you say a great simplifying of understanding DoF.
 

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