Scanning 11x14 BW Negatives

[rawitz]

Alan - consider this:
4x5 film
96mm x 120mm
Theoretical diffraction limit at f/22 is 70 lp/mm

Hm, please give us the formula for these results. And do you calculate the "critical aperture" or the "beneficial aperture" here?
As I can reconstruct, you give us the convential "beneficial aperture" f22 for 4x5 (diffraction unsharp circle 0,1mm or 5lp/mm for 4x5) but calculate further for 8x10 with the "critical aperture". Thats fully unlogical.
For the "critical aperture" calculation of 70 lp/mm on film I must calcule a f=4 stop, this is a 3600 dpi scan or corresponding a 200 Mp-camera.
No LF can work with f-4 in practice.

regards
Rainer

[Corran]

I have no idea how you arrived at the discussion of f/4 for LF photography. In practice it doesn't matter what the theoretical diffraction limit is at f/22, it will be half as much at f/45 due to the physics, and the calculations end up in the same vicinity as above with similar max print sizes from the given formats. The 70 and 35 lp/mm figures are just what I've seen calculated for the highest possible resolution at those apertures and of course will be generally affected by other considerations like lens quality, film flatness, etc.

The online "DOF Calculator" shows exactly the same DOF for the two formats of 4x5 and 8x10, when equalizing lens choice and aperture and using a larger CoC for 8x10 due to needing less enlargement to make the same print size.



If you don't need as much DOF and can keep f/22 on both 4x5 and 8x10 (flat subjects or some other reason) then yes 8x10 will yield "sharper" enlargements. In practice some photographers may need more or less DOF. My subjects tend to need as much DOF as possible even given the ability of tailoring DOF with movements - when trying to optimize apertures for resolution I would often have softness from the lack of DOF, more so than diffraction effects would've shown at smaller apertures. I did try this, after some criticized the apertures I used with ULF, and found I was absolutely correct in my need for DOF.

When in doubt, stop down!

[Sal Santamaura]

On the contrary, assuming a fully functioning human eye-brain system, extreme depth of field with everything sharp perfectly replicates reality. Our eyes scan what's before us and focus ("accommodate") to every part of the scene at all distances. We continuously move our gaze to elements of interest and the center of our eye renders them in sharp detail. The only way a photograph can simulate reality is to ensure that, regardless of what part of it we look closely at, it's in focus and detailed.

Of course, those with uncorrected vision defects might have an alternative concept of "reality." Whether optical or other aspects of perception.

...the normal human eye does not have infinite DOF from 2" from their nose to infinity in focus, all the time (not when you turn your head and scan and focus on different things that's not what I was talking about)...

Of course the human eye doesn't have infinite depth of field. I never claimed it does. That's not what I was talking about. As I wrote, the only way a photograph can simulate reality is to ensure that, regardless of what part of it we look closely at, it's in focus and detailed.

...I guess this sort of "hyper reality" (not only extreme DOF but vivid saturated saccharine colors &c ) is what most LF photographer's "go for"...

Exaggeration of contrast in black and white and saturation in color are things that some large format photographers do to attract attention from the easily impressed. The proverbial "pop." I don't do them, and am not sure one can even conclude that "most" large format photographers do.

...extreme DOF all at once is an alternative concept of reality ... a photograph it's a thing, it's not reality...

Everything-in-focus is neither an alternative concept of reality nor reality itself. As I wrote, it's an effective way to simulate the reality of how humans view the world, using their eyes (including accommodation) and, sometimes, necks. Note that within a limited field of view, such as one photographed with a long focal length lens, humans can often completely scan the real-world scene without turning their heads at all.