Use of f32 and f45 for 4X5 landscapes

[Roger Rouch]

An after thought - would it be that lenses with a larger image circle - as in greater coverage would in general tend to give better results at these small f-stops? It is interesting that the lens tests I've seen tend to stop at f22.

[Wayne_6692]

In response to your last questions. The lenses with a larger coverage may give better results due to a flatter field when the image field is smaller than that for which it is designed ("sweet spot"). And as far as publishing lens test results for apertures smaller than f/22 there's really little point in doing that. By f/22 diffraction is the dominant abberation in any decent lens - publishing such lousey- looking numbers (which are an unavoidable fact of physics) doesn't make a good impression on the less-informed consumer, and really doesn't tell us anthing of use.

[nick rowan]

I have always wondered this: if f/16 or f/22 is the sharpest aperature-setting on most large format lenses, why was "f/64" adopted by Ansel Adams, Edward Weston, and certain other photographers of the "f/64 Group" in the 1930's as the ultimate expression of sharpness and resolution in a photograph? Or were the members of this group more interested in the extended DEPTH-OF-FIELD specifically, afforded by an f/64 aperature--and that this outweighed any loss of sharpness and resolution that may ensue from stopping down so far? Or is f/64, in fact, the sharpest aperature on most 8 X 10 lenses (as opposed to 4 x 5 lenses)? Or was it just deliberate exaggeration on their part, for literary effect?

[Wayne_6692]

Nick - Those photographers used 8x10 cameras (as well as odd-sized formats that are no longer around) and mostly made contact prints. Once you start using the long focal length lenses common in 8x10 depth of field decreases dramatically - they chose the smallest f/stops usable that would still give acceptable sharpness. I've continued my testing and for the lenses that go to f/64 I have the following results on a 5x7 format (aerial resolution - results on film may differ). 150 Super Symmar XL: C/E- 23/18, 210 Apo Symmar: 23/19, 150/265 Convertible Symmar @265: 23/10, 305 G-Claron 20/20, 450 Fuji 12.5C: 22/22.

You can see that the resolution figures are for the most part the same - diffraction has done it's dirty work. Even @ 20lpmm though you have room to enlarge 2x-4x (depending upon your tastes) and get an acceptable print. Don't forget, these figures are for the plane of the focused image, once you induce the losses for divergence away from this ideal plane the resolution goes even lower. In response to Adams and his friends there was another group that called itself f/128 - wonder what happened to them?

Wayne

[Patrick Raymore]

My solution to the depth of field problem springs from the saying "you can not be too rich, too thin, and you can't have too may film holders". If in doubt I just shoot an extra sheet of film at a smaller aperture (exp. f32). At worse you have wasted a sheet of film and learnt a little. At best you will be thankful later because the first sheet did not have enough depth of field. Let's face it, compared to the gasoline, cost and effort it took me to get there, one more sheet of film isn't that much to pay for a little insurance. Go ahead live it up a little. And yes, get a few more holders.

[ImSoNegative]

when shooting 4x5 with wide angle lenses, 65mm, 75mm etc. i can get everything sharp usually at f16, sometimes f22, with my 203 ektar i usually have to stop down to f32 depending on what im shooting. on my 8x10 my minimum is f45 to get everything sharp that is with a normal lens 300mm.

[Doremus Scudder]

Several things to address here.

First, choosing focus points when using tilts is often tricky. Having a good mental picture of where the plane of sharp focus is in a scene is needed. It is also important to know that when the plane of sharp focus is not parallel to the film plane, the depth of field is wedge-shaped, with the shallowest part closest to the camera position and widening with distance. Positioning the plane of sharp focus so that other objects in the scene are as close as possible to it isn't good enough. One has to ensure that near objects not in the plane are closer to the plane of sharp focus than ones more distant (I hope that's understandable, it's a bit difficult to formulate...).

After one has positioned the plane of sharp focus, one should focus on objects outside the desired plane and note the focus spread. When using tilts, it often happens that near objects that are just out of the plane of sharp focus require more racking in or out to get in focus than distance objects that are much farther from the focus plane. When using the near-far method for focusing, you need to really be careful to use the objects that require the most deviation in the focusing in both directions from the desired focus position to calculate the needed f-stop. It's unfortunately all too easy to ignore a depression in the mid-field or a close vertical object and end up having them rendered out of focus.

I highly recommend the method of selecting the optimum f-stop described in the following article. http://www.largeformatphotography.info/fstop.html

Once you've become proficient at determining where the plane of sharp focus goes for minimum focus spread and placing it there, it becomes a rather technical matter of simply measuring focus spread, selecting the right f-stop to keep things sharp and then calculating exposure.

I might add that I use f/32 and f/45 for 4x5 shooting as much or more than John Sexton... It becomes quickly apparent that, if one wants depth-of-field and everything sharp, that most subjects require fairly small f-stops.

Also, a bit of diffraction is, for me, much more acceptable than out-of-focus portions of the print that I really wanted in-focus.

The other side of this coin is the final print size. Small prints can be made from negatives taken at really small apertures and show no degradation at all due to the limitations of enlarging lens, paper and degree of enlargement, not to mention the inability of the human eye to resolve much more than 5 lpm. In larger prints, diffraction may show, but will often be not noticeable due to the larger viewing distances. This may be acceptable for some. However, if we assume a standard viewing distance of 18 inches or so, there will also be an optimum print size for apertures smaller than the best for the lens in question. Practically, this means that for shots made at apertures smaller than f/22, the maximum acceptable print size decreases in proportion to the diffraction degradation introduced. Shots made at f/32 will usually print to 16x20 acceptably, but for some subjects a bit smaller might be good. It is largely subjective at some point. Nevertheless, it is quite possible to make an 11x14 print from a negative shot at f/45 on 4x5 film (assuming we are using close to the full negative) and be well over the resolution limit for human sight (i.e., sharper than we are able to see).

Don't hesitate to use smaller f-stops if you need them, but make sure you really need them first. I often start over with camera movements or do some adjusting when my focus spread is too great, and often manage to end up with an improvement, allowing a bit larger optimum aperture. Sometimes, however, I just have to shoot at f/64 and then mark in my exposure record not to enlarge more than to 11x14.

This is kind of a general ramble, but I hope it contains some information useful to the particular problem the OP addressed.

Best,

Doremus Scudder

[Brian Ellis]

IMHO, based on a certain amount of testing, diffraction isn't a major problem with 4x5 film and prints in the approximate 20x24 range or smaller. Use the aperture you need to get the depth of field you want (after making whatever camera movements you plan to make). Don't worry about diffraction unless you're using a smaller format or plan on making a print larger than 20x24 (or somewhere in there).

Use the method of aperture selection described in the article Doremus Scudder cites, which IIRC is the same method that Paul Hasma (sp?) described in his well-known Photo Techniques article many years ago (sorry, I no longer have the article so I can't provide a cite), and you'll have a fool-proof method of selecting the aperture that will give you the depth of field you want while minimizing the effects of lens aberrations (which tend to be worse at wider apertures) and diffraction (which is worse at smaller apertures).

There are few practices more detrimental to technically excellent photography with a LF camera IMHO than arbitrarily stopping down to f45 or f64 to make sure you get the necessary depth of field or never stopping down that far because you're worried about diffraction.

[Drew Wiley]

If you like sharp prints, stopping down a 4x5 lens to f/45 or f/63 will definitely result in
loss of sharpness due to diffraction, and this will be visible in a 16x20 or larger print.
You'd be fine at f/22 or f/32 however. Just depends on your standards and scale of
reproduction. With 8x10 film the comfort zone is around f/45 to f/64, but the degree of magnification on the same sized print is far less too. Just because John Sexton
stopped things way down doesn't make it sensible for most of us - often he prints no
bigger an 11x14, and some of his images were intended for books, where the scale
of magnifcation is also quite modest.

[Maris Rusis]

After a few thousand sheets of 4x5 and 8x10 film and a few hundred conversations with viewers I've come to the conclusion that I'm actually trafficing in apparent sharpness rather than on-film resolution. Even photographs that I know are a bit soft get called "sharp" if:

They have consistent sharpness all over. Out-of-focus is a far bigger killer of apparent sharpness than diffraction.

The foreground details are sharp even if the distant stuff is a bit soft. The reverse, soft foreground and sharp distance, looks really bad in comparison.

There is fine high contrast detail just above the resolution limit. The best pinholers play this game beautifully.

The ultimate diffraction-resolution trade-off happens on 4x5 film enlarged to 8x10 at about f300. Pinholes and lenses deliver the same detail. Presence or absence of glass makes no difference.