What is the ideal aperture?

[Lightbender]

At what aperture do you get the maximum depth of field without sacrificing detail to diffraction?

[mdarnton]

Someone the other day specified 6mm more or less. I like the idea, so I hope it's right!

[Jac@stafford.net]

At what aperture do you get the maximum depth of field without sacrificing detail to diffraction?

Generally (which means most, not all) LF photographers to not worry about diffraction. The degree of enlargement and viewing distance are the significant factors. IOW, worry not.

It is something that miniature and MF photographers find difficult to grasp at first.
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[Jac@stafford.net]

Someone the other day specified 6mm more or less. I like the idea, so I hope it's right!

OMG, that might have been from my post decades ago. Specific aperture diameter seems to have a congruence with format size, enlargement and viewing distance. Six mm is, therefore, not a universal metric.
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[mdarnton]

Maybe I caught it in some of my web searching. I think it was, in fact, you. I just looked on one of my Nikon lenses that I know precisely where it starts to go haywire, and 6mm it was! It doesn't sound too bad for longer lenses, either. I'm not so sure about my 15mm Heliar for 35mm, which may be smaller than that to start with. :-)

[Mark Sawyer]

At what aperture do you get the maximum depth of field without sacrificing detail to diffraction?

It depends on, (among other things), the degree of enlargement. Edward Weston used a pinhole aperture (and all day exposures) to get maximum depth of field in some of his larger-than-life-size still lifes of vegetables and seashells. Any larger aperture would have given out-of-focus areas, and because he contact printed, the detail is as fine as the eye can see.

[Ken Lee]

At what aperture do you get the maximum depth of field without sacrificing detail to diffraction?

Forum member Emmanuel Bigler (a professor of Optics) has written about this subject here several times. Here's a sample:

"I have done a compilation of the best f-number recommended by view camera lens manufacturers and we can summarize by the following rule of thumb for classical standard lenses :
N_best = f(in millimeter)/(8 millimeters)...for top-notch modern 6/4 lenses of the last generation and razor-sharp expensive "digital" view camera lenses the rule of thumb would be closer to f(in millimeters)/(11 millimeters)...The consequence is that a good standard 50mm lens designed for 35 mm photography should not be stopped down beyond f/5.6 or f/8, whereas a 150mm lens designed for 4x5 can be stopped down to f/16 to f/22, a 210 mm for 5x7 : f/22 to f/32, a 300 for 8x10 : f/32 to f/45. Assumed that the enlarginf factor is reduced in proportion, of course, for the same final print size."

See Diffraction large format vs smaller for the discussion.

With a good loupe we can point the camera at a detailed subject, inspecting the ground glass as we stop-down the lens. Resolution will reach a peak, after which it visibly declines. That's an empirical rather than theoretical approach.

It's one thing to know the aperture beyond which resolution declines: it's another thing to decide where we want to draw the line for a given image. Are we making contact prints or enlargements ? Can we apply digital sharpening ? From what distance will the image be viewed ? ... etc. Ultimately, we get to decide.

[ic-racer]

http://www.largeformatphotography.info/fstop.html

[mdarnton]

Forum member Emmanuel Bigler (a professor of Optics) has written about this subject here several times. To summarize his recommendation, we can divide focal length by 11 to get the number.

[INDENT][I]"...for top-notch modern 6/4 lenses of the last generation and razor-sharp expensive "digital" view camera lenses the rule of thumb would be closer to f(in millimeters)/(11 millimeters)...The consequence is that a good standard 50mm lens designed for 35 mm photography should not be stopped down beyond f/5.6 or f/8, whereas a 150mm lens designed for 4x5 can be stopped down to f/16 to f/22, a 210 mm for 5x7 : f/22 to f/32, a 300 for 8x10 : f/32 to f/45. Assumed that the enlarginf factor is reduced in proportion, of course, for the . . .

In short, using his numbers, around 7mm. Slightly higher standards than Jac, maybe. :-)
I suspect he should have used a wider range of examples than just a bunch of "normal" lenses. :-)

[Jac@stafford.net]

In short, using his numbers, around 7mm. Slightly higher standards than Jac, maybe. :-)
I suspect he should have used a wider range of examples than just a bunch of "normal" lenses. :-)

See the reference to Emmanuel Bigler, and big thanks to mdarton.
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