8x10 photography and diffraction

[StuartR]

Hi everyone. I am a fairly recent convert to 8x10 photography, after a lot of time spent doing 4x5 and smaller formats. In general, I try to maximize the technical qualities in my work. Art first, of course, but performance is also very important to me. I work as an artist and exhibition printer, and in some recent shows I made murals that were 170x220cm. I am interested in trying to get the best technical results out of 8x10, or at the very least, understanding the techniques for getting the best technical results out of 8x10, so I can either employ them or ignore them for any given picture. I do not intend to enlarge every piece to gargantuan proportions, but I would like to know how best to do so if for a certain piece I would like to.

So. I have found that with my lenses, I get the best image quality at f/16-f/22 with 4x5. In certain narrow cases, f/11 can be slightly crisper, but generally DOF is an issue at that point. Starting 8x10, I tried f/22 as a baseline, and while the results are acceptable, in general the performance upon close inspection is not as good as on 4x5. Obviously the negative is 4 times the size, so it will be better in the end, but I am wondering what the real "best" apertures are for 8x10 with very large enlargements. I understand that maximizing depth of field might require f/64 or greater, but I am guessing that for normal subjects that is quite soft. I know this is hard to generalize about, but assuming a very good modern 8x10 lens like the 300mm f 5.6 Fujinon CM-W (which I have), the 450mm Nikkor M (which I am looking at), what is the optimal aperture for large enlargements? f/22-f/32?

[JyL]

Bonjour,
On principle, it seems to me that using a given optics the result must be the same regardless of the film format used.
Why would it be otherwise?

[StuartR]

Bonjour JyL. You are of course correct! I am just trying to get an idea of at what sizes does it really start to come into play in 8x10. Since the enlargement ratio is significantly lower, is it ridiculous to worry about the loss of sharpness at f/45 or f/64? Or is that something that is visible in larger prints? I do not have a drum scanner, or I would test myself. I am also not sure if it is just my lens (300mm 5.6 CM-W) which is not as sharp as my 4x5 lenses (the best of which is a 110mm Super Symmar XL).

[Oren Grad]

In general you should not expect lenses designed for 8x10 to perform as well on close inspection as lenses designed for 4x5 - remember that they are designed to cover a much larger image circle. The quality improvement from using larger formats comes from being able to use smaller enlargement ratios to achieve a given final print size.

FWIW, Rodenstock used to recommend f/16-f/22 as overall "best apertures" for 4x5 and f/32-f/45 for 8x10.

That said, you really need to run your own tests to see for yourself what the image character is like at your preferred enlargement ratios and decide what will suit your purposes. Our lenses are not the idealized optical systems on which theoretical resolution calculations are based, and it's not always straightforward to model the subjective perceptual effects of the diffraction patterns generated by non-circular diaphragm shapes along with the particular mix of residual optical aberrations allowed in each lens design.

Remember that you don't necessarily have to spend the $$$ and darkroom/lightroom effort for a series of big prints to do this - enlarging to smaller paper from carefully-chosen crops may tell you most or all of what you need to know.

[Bernice Loui]

8x10 is not an ideal film format. It is widely believe the larger sheet of film and lower magnification ratio will result in the very best enlarged prints. This is not so simple or idea once all factors in the print making process is considered. This was the conclusion after burning a LOT of 8x10 film and making prints back in the late 1980's and early 1990's.

8x10 and larger is ideal and best for contact prints.

Difficulties with 8x10, which has been posted numerous times here:

*Choice and availability of optics-lenses. The very best modern and vintage lenses that are optimized and designed for 8x10 is pricey and currently in high demand. Add limited number of optics-lenses that have historically been specifically designed for 8x10 is limited.

*Film flatness, is a challenge with 8x10. While there is mention of adhesive and vacuum film holders, consider if this is actually practical in real world image making.

*Camera alignment become crucial if larger lens apertures are to be used. Taking apertures with the exception of soft focus and highly selective focus images. Typical taking aperture for 8x10 will be f22 and smaller which puts a, "way Nature actually is" limit on possible resolution. There is a belief-mind set that "stopping down" will cure most and the film size will make up for that. This is simply not true.

*As the image ratios move towards life size, the larger film format will begin to experience great difficulty with depth of focus-depth of field. Images made at true infinity focus is not really a problem as the largest format can be used with the largest lens aperture with excellent results (historical aero recon film images made on BIG sheet film support this assertion) once images are no longer made at infinity, the larger the film format, the greater this problem.

*Then there is camera system size-weight, carrying loaded film holders, film processing, 8x10 enlarger and wet print making system and .... Once all this is considered, 8x10 is no longer so simple or ideal.


-Point being, go one film format size down to 5x7 or 13x18cm and most if not all these problems are reduced significantly.

-Ideal LF film format lens apertures are typically f8 to f32, smaller taking apertures will be impacted by they way Nature really is, how Nature will enforce its ways regardless of the technology involved to exploit the way Nature really is.


There is vast initial visual appeal to sheets of color or B&W film images, this is one of the prime reasons for some to be so drawn to 8x10, technically, the realities of print making with 8x10 often comes with a slow realization of what the very real limits of 8x10 is. I'll say this again in the face of much opposite here, 4x5 is IMO too small a sheet film format for very high quality projected film images. The projected print image made using the very best 4x5 is lesser than 5x7 or 13x18cm with 8x10 often experiencing a different set of problems.



Bernice

[Bob Salomon]

Are you trying to make mural size prints? If so, do you print with an enlarging lens designed for murals rather then a standard enlarging lens? An example would be a Rodagon G.

Are you printing with a glass carrier?

[Corran]

IMO 4x5 is the best compromise between size of film and technical limitations. However you don't tell us what type of images you are making. As someone who primarily shoots landscapes out in the real world, DOF and exposure times are an issue and the larger the format the more of a problem this becomes.

If you are shooting flat-field work or some other type of images where moderate apertures are okay, perhaps you can eke out a bit more resolution - and only if your lens performs that well at those apertures.

There is no free lunch.

[Sasquatchian]

Diffraction affects large format exactly the same as smaller formats, you just don't see its effect on small to medium sized prints. If you look up resolution charts for various large format lenses, you can easily see where most of them peak at f/11 - f/16 and start falling off from there. What you really have to look at is the relationship to corner and edge performance to center performance, and that's where the compromises happen. You might see that center performance drops off considerably at f/22-f/32 but the corners have come up considerably as well, providing a more balanced performance across the frame, even if you gave up some central detail.

I used to drum scan 8x10 chromes for a well known car photographer - twenty years ago, and every single one of those was soft even to the naked eye - because he shot them at f/64-f/90 for maximum depth of field. But the agencies insisted on 8x10 and 8x10 is what they got, sharp or not.

In another situation with a friend who designed and built his own custom aerial 8x10 camera, I helped him judge the test images to see when the lens was sharp enough for his purposes - which were six feet by eight feet Lightjet prints. The fixed focus aerial lens needed to be stopped to f/11-3/4 to be acceptable in the corners. Shooting Portra 400 pushed a stop let him get to a barely acceptable shutter speed for hand holding this beast standing on the skid of a Jet Ranger.

[Pere Casals]

what the real "best" apertures are for 8x10 with very large enlargements.

In practice, with good 8x10 "modern" lenses try to keep aperture around f/16 or f/22 when center sharpness is the important thing, depending on the particular lenses, for optimal corners or to get necessary DOF you may have need stop more.


___________________


The 8x10 optimal aperture for best image quality mainly depends on 3 factors:

1) Lens performance. A 1930's 8x10 glass may have optimal aperture at f/45 and a recent model may have it at f/22. Each glass has it's optimal aperture.

2) Your subject, if you shot a distant mountain then you may have all in perfect focus, so you may use the optimal aperture of the lens. But you may have different objects at different distances so you may need DOF management skills, including movements.

3) Importance of sharpness in the corners, for your image.



1) Lens performance

Many 8x10 modern lenses (those made in the say last 40 years) are diffraction limited by f/32, and some at f/22, so optimal aperture may be at around f/16 in some cases, beyond optial aperture, you know, you start damaging Image Quality, specially in the center, while usually for optimal results in the corners an smaller aperture would be better.

Here you have some tests made by Mr Croell, see for example the fujinon C 300, that sample was better at f/16, for 4x5. As tests are done for 4x5 this not says how 8x10 corners are. https://www.arnecroell.com/lenstests.pdf

You may learn to measure lens performance in lp/mm in practical conditions to see how your particular glasses do behave.


2) Your subject

You may use a DOF calculator mobile app to know the theoric circle of confusion at each distance and when this is limiting the lens performance, you should learn when lack of DOF is degradating image beyond what lens is able, in that way you will understand the good diffraction vs DOF balance for your glasses.




3) sharpness in the corners

If you have sky in the top corners and moving water in the bottom corners, or top corners are simply OOF, then you may stop for optimal center rather than for the +optimal average.

[Drew Wiley]

That's a significant enlargement, but not terribly big for 8x10 film. There are much more important things to think about first before potential diffraction issues in a taking lens, namely, how to keep film flat in the film holder to begin with (can be done, but don't take for granted that an ordinary holder will do it), management of more serious depth of field issues than in 4x5 photography (which generally mandates smaller apertures), and precise enlargement afterwards in the darkroom itself, or equivalent scanning precision. I really wouldn't worry about anything in the f/32 to f/45 range with those lenses. Diffraction starts getting apparent at f/64 upon close inspection. If one can spot the difference on non-enlarged 8x10 film, like Sasquatchian noted, then something else is wrong instead. Don't be scared of 8x10. I've done lots of high detail work with 8x10; and the results truly can be visibly superior to 4x5. But there's a learning curve to it. The logistics of 8x10 are somewhat different from 4x5, as well as realistic depth of field control. Then, if you happen to print on something like inkjet rather than optically, you have to ask yourself if the bigger format is worth it, since inkjet itself is not as high a resolution medium as direct enlargement. But there are a couple of things I disagree with Bernice about, though what he states in general is relevant. Vac or adhesive film holders are completely practical in the real world. And my own real world includes a lot of harsh terrain and bad weather. That's how I've been doing it for precise 8x10 work now for decades (vac in the lab, adhesive outdoors); there are numerous previous threads how to make and use these. There are plenty of good lenses to choose from. Some are expensive and some are a bargain. 8x10 cameras differ in quality, precision, and rigidity; so you have to think about that too. Think logistically in terms of travel - what you really need and what you don't. Try to keep lens weight down if you have to carry equipment. Heavy lenses also affect image accuracy at long bellows extension if a front lens standard is not especially rigid. You'll need more serious tripod support, etc. Nikkor M lenses are wonderful; but in the 450 length, I prefer the Fuji 450C for its much lighter wt. Most 300mm lenses are going to struggle with the larger image circle
necessary for 8x10 using serious rise or tilt unless they are well stopped down. So you can forget about nitpicking "ideal" lp/mm or "optimal" aperture. It doesn't mean much unless you're doing flat copy graphics work. Otherwise, just try the excellent lens you've already got in that focal length, and if you absolutely need more image circle, think about a 360mm lens instead.