Curiosity testing for diffraction limitation -- very general

[Doremus Scudder]

IM-HO, depth-of-field always trumps diffraction degradation.

The visible effects of diffraction in a print depend not only on the (effective) taking aperture, but also the degree of enlargement, viewing distance and visual acuity of the viewer. In many cases, the slight overall loss of acutance caused by diffraction may not even be objectionable, depending on the subject and the intent of the photographer.

As far as I'm concerned, even with a worst-case scenario, e.g., a close-up taken at, say, f/45 on 4x5-inch film and enlarged to, say, 11x14, the loss of sharpness due to diffraction is much preferable to annoying out-of-focus areas.

Of course, we always try to optimize sharpness by choosing our viewpoint carefully, using movements, etc. in order to get as close as we can to the magic f/22. However, I don't hesitate to stop down to f/32 or smaller if I need it for DoF. I think I have a lot more photographs made at, or close to, f/32 than any other aperture. I don't see a practically significant loss of sharpness in prints up to 16x20.

Sharpness isn't everything...

Best,

Doremus

[Drew Wiley]

Does that tip of nose to base of ear dogma apply to shots of Jimmy Durante too? Is there some nose-to ear depth of field chart or app, with a nose-length caliper included? Who cares what someone was taught? Great portrait photographers like Julia Cameron and Steichen tended to focus and stop down to the where it simply felt right on the groundglass, esthetically, for them personally. Even the softening effect of diffraction has been deliberately used by some. Conversely, many use out of focus areas deliberately and intelligently. No rules.

[Bob Salomon]

Does that tip of nose to base of ear dogma apply to shots of Jimmy Durante too? Is there some nose-to ear depth of field chart or app, with a nose-length caliper included? Who cares what someone was taught? Great portrait photographers like Julia Cameron and Steichen tended to focus and stop down to the where it simply felt right on the groundglass, esthetically, for them personally. Even the softening effect of diffraction has been deliberately used by some. Conversely, many use out of focus areas deliberately and intelligently. No rules.

But what you see on the gg doesn’t necessarily show you what an enlargement would look like!

[ic-racer]

When I tested for diffraction using my equipment, the relative effects viewed under the enlarger, approximated the results of in-camera tests.

To be more specific. For each format I tested, I could approximate the in-camera effects by watching grain, in real time, under the enlarger lens as the lens is stopped down.

EXAMPLE:

35mm film enlarged with a 50mm lens. Analyzed with a grain focuser. Enlargement to a 'usual' size like 8x10. Right about at f8, the grain starts to get fuzzy. This approximated what my in-camera tests showed.

Similar with 4x5 film enlarged to 11x14 with a 150mm lens. Grain is much harder to see, but seems to get fuzzy around f32.

8x10 is very hard to do the test because grain is hard to see but for a 16x20 enlargement, grain gets fuzzy around f64 and this was similar to in camera tests.

[ic-racer]

I think most of the posters in this thread are pretty experienced photographers know of the the focus method of Hansma,( it is on this foums main page.) Just to emphasize that method is designed to provide the best compromize between airy disk size (diffraction) and defocus (depth of field).

When I first tried it I was convinced it would be a FAIL when apertures were recommended for my focus depth beyond my 'known' diffraction limits I determined in post #14. However as others, like Dormeus pointed out above, the method really does give excellent prints.

the loss of sharpness due to diffraction is much preferable to annoying out-of-focus areas. --D.S.

[Ulophot]

Thanks again to all; I appreciate both facts and feelings. However, I would like to ask one more question, since, not finding the answer in searches, I made a calculation on my own, which is bound to be wrong unless I got lucky. Again, friends, this is primarily curiosity, since my portraiture comes first and, as I said originally, my two lenses are more than adequate.

For illustration, one may refer to two photos from my cited garden work, both posted in the last couple of days (it's July 14, 2020 today), in the "Flowers Anyone?" and "Just Leaves" threads.

Based on Bob Solomon's initial reply to this thread, I am trying to figure out how to calculate reproduction ratio. I am simply trying to have in the back of my mind what subject distance with each lens starts falling below the 1:10 general consideration that Bob mentioned. Am I worried about it? I am not; I am simply curious, and I like to know my equipment. I hope I have emphasized enough that my interest is not not a critical one in this matter.

Here's what I did: If I have a 6' length covered on the long dimension of my 4x5 film, I am reducing 72 inches to 5, approximately. 72/5 = 14.4. Therefore, my magnification ratio is roughly 1:14 at whatever the subject distance is with that lens. If that's right, then, for instance, in my Hydrangea image in "Flowers", a ~4"-long leaf, essentially parallel to the film plane so that it's length is not foreshortened, which measures 1" on the GG, means the ratio is 1:4. With such an approach, I can easily find out subject distance for a given approximate repro ratio.


Am I calculating correctly, for general approximating purposes?

Thanks.

[Ulophot]

Hi, Alan, thanks for your reply. In my portraiture now, my considerations area bit different. I spent years photographing in studio, and when I returned to photography a few years back, I had decided to use natural light, or existing light, as much as possible, and leave the studio for location work, i.e., with my subjects in their own environments. So far, I have tended toward framing which includes more of the subject and something of the surrounds, so that my DOF considerations are different from what often works so well in more head-and-shoulders or closer kinds of framing.

As mentioned in my initial post, it was closer-up photos made in my garden, of plants (which allowed me to photograph without a mask on myself or the plants), that led me to consider the practical effects of diffusion limitation with my particular lenses.

[Bob Salomon]

I used a ruler or a yardstick and measure its length on the gg. But a much easier way is with the Rodenstock DOF/Scheimpflug pocket calculator.