Optimum shooting apeture for 4x5

[stompyq]

I've been curious about this for a while. Theres a lot of information out there but non of it gives a clear answer. I routinly avoid going bellow f/11 with my DSLR b/c of diffraction induced loss of sharpness, and only go below when it's unavoidable (i still take a shot at f/11 too). I've been largly shooting at f/32 with my 4x5 gear Sometimes going to f45. Most of the time i do this not b/c of DOF but to avoid timing a shutter speed of 2 seconds or something (much easier to time 5-10 sec than 2 sec). Do you think I am missing out on sharpness? or is it a non issue with LF?

[Ash]

I'm no expert, my 4x5 hasn't even arrived yet(!), but I think I read on the page here (http://www.largeformatphotography.info/fstop.html) about it. If you aren't enlarging to huge sizes, then it's less important I think, but there's the reading if you want to research.

[Jim Jones]

Ash's link is a great source of information. There are simpler approaches, though. When a print is viewed from the distance that gives correct perspective, the camera lens aperture can be stopped down to a linear diameter (as viewed from the front of the lens) of about 5mm before diffraction begins to be noticable.

However, prints are rarely viewed in the correct perspective. Telophoto prints are usually viewed from a closer distance, and require larger linear apertures. The reverse is true of wide angle lenses. At f/11 a Nikkor 20mm has an aperture less than 2mm, while a Celestron C8 telescope with a focal length of about 2000mm has a fixed diameter of 200mm. Yet, prints from each are often viewed at similar distances.

When one usually prints at a fixed size, and the prints are usually viewed at the same distance, a depth-of-field scale can be calculated and attached to a view or press camera. This scale will be valid for all focal lengths as long as long as print size and viewing distance are constant. The articles by Stephen Peterson and Paul Hansma cited in Ash's link provide more information on this. The DOF calculator in Masayoshi Hayashi's article http://www.largeformatphotography.info/dofknob/ might be adapted to dissimilar cameras. Keep in mind, despite the mathematics often used in discussing depth of field, it is much more subjective than objective. The DOF scales once common on 35mm cameras were too critical for most snapshots, and too optimistic for much serious photography.

[Brian Ellis]

IMHO diffraction is a non-issue with 4x5 film and enlargements of about 4x or less. The whole diffraction thing is a big deal with 35mm because the enlargements are usually in the range of 8x and higher. That's why 35mm lenses typically have their smallest apertures at f16 or f22. But with 4x5 I don't think it's an important consideration in selecting your aperture, at least not until you get above 4x enlargements. So I'd suggest just using the widest aperture that provides the depth of field necessary to make the photograph you want to make. There are tables that allow you to determine that, if you're interested I can dig up a cite to the one I use. But for most general photography purposes that will be an aperture smaller than f11.

For times in the 2-3 second range I just use the "one Mississippi, two Mississippi" thing, which seems to work fine. Being a half second or even a second off of a 3 second exposure isn't usually critical, especially not with negative film.

[Ole Tjugen]

I believe I've used every possible aperture from f:3.5 to f:128 without ever having noticed loss of sharpness from diffraction.

[GPS]

For times in the 2-3 second range I just use the "one Mississippi, two Mississippi" thing, which seems to work fine. .

If you want to be less talkative, for the 2 seconds exposure you can use the simple: "Miss Mississipi". Works fine.

[Steve Hamley]

You're not in Kansas anymore Stompyq. The larger the format, the less depth of field for an equivalent view, because the lenses get longer. 300mm for 8x10 versus 50mm for 35mm. Stop down until you get the depth of field you need - otherwise you'll have the sharpest fuzzy pictures you've ever seen.

Steve

[Jim Jones]

I believe I've used every possible aperture from f:3.5 to f:128 without ever having noticed loss of sharpness from diffraction.

The one time I needed to use a 540mm lens at f/128 on 5x7 film, 2.5X enlargements weren't perfectly sharp. One formula indicates 6 line-pair/mm on the print. Focus shift may have been an additional contributing factor.

[Donald Miller]

While I will not argue what others view as being acceptable, I will say that my optimal minimum aperture for 4X5 is F32 and my minimum optimal aperture for 5X7 is F45 and my optimal minimum aperture for 8X10 is F 64. Anything smaller than that, expecially on 4X5 above an 11X14 print, and I begin to see the effects of diffraction. Maybe my standards are more stingent than some. But this is what I have found in my experience.

This standard of mine requires using a view camera's movements optimally rather than simply stopping the lens down to achieve suitable depth of field.

[Leonard Evens]

You can stop down more with a 4 x 5 image without diffraction being a factor because you have to enlarge less for the same size final image. The effect of diffraction is the same in either case at the level of the image in the camera, but enlargement magnifies it. If you enlarge less, you can stop down further. The effect can be estimated by taking the ratio of correpsonding format dimensions. My Nikon D70 has a diagonal of about 28 mm. A 4 x 5 frame has a diagonal of about 153 mm. The ratio is about 5.5. So if I were comfortable with f/11 with my D70, I should be comfortable with f/(5.5 x 11) or f/55 in 4 x 5.

What happens when you go from a smaller to a larger format is that you gain extra usable stops as far as diffraction is concerned, but you lose the same number of usable stops as far as DOF is concerned. The number of usable stops stays the same, but you end up having to use longer exposure times because of the shift of the range towards smaller apertures.

[stompyq]

You're not in Kansas anymore Stompyq. The larger the format, the less depth of field for an equivalent view, because the lenses get longer. 300mm for 8x10 versus 50mm for 35mm. Stop down until you get the depth of field you need - otherwise you'll have the sharpest fuzzy pictures you've ever seen.

Steve

:) Thanks every one for the great replys. I think i finaly see what i am doing. Leonard thanks for making it so clear. Even my thick skull got what your talking about!!

[steve simmons]

View Camera did a two part series on How to Optimize the Sharpness of Your Photographs in the July and Sept 06 issues. It is much too long to summarize here. The author is Dr. Robert Hallock, a physics professor, who teaches optics and creativity to photographers

steve simmons

[Neal Shields]

In "Post Exposure" (on page 2, so he must consider it fairly important) Ctein takes up the issue of sharpness expressed in Lp/pm.

For an 8x10 print he defines 5 lp/mm as "adequate sharpness": "the point at which most viewers say; "it's sharp".

However, he talks about the fact that professionals and hobbists are not "most viewers" and goes on the talk about "perfect sharpness".

Emperically he shows that the human eye can only resolve up to 10 lp/mm however in testing people can tell the difference in prints up to 30 lp/mm.

He attributes this to a preceptin of acutance.

"in other words, the ressolution difference between 10lp/mm with sharp edges and fuzzy ones is way down around 30lp/mm"

I think that this is very important because the 6lp/mm standard is used to justify the fact that most modern printing equipment prints at 300 dpi. If you can't see the difference between 300 dpi and 400 dpi why bother, goes the logic.

However, if in side by side compairisons most viewer can tell the difference between a print exhibiting 6 lp/mm detail and one exhibiting 30 lp/mm detail, than large format makes sense and most digital cameras were obsolete while they were still a gleam in their designer's eye.

Ctein, if you read this please post page 2 and 3 somewhere so that I can link to it, I think that for today's audience, they are two of the most important pages ever written on photographic technique.

[stompyq]

View Camera did a two part series on How to Optimize the Sharpness of Your Photographs in the July and Sept 06 issues. It is much too long to summarize here. The author is Dr. Robert Hallock, a physics professor, who teaches optics and creativity to photographers

steve simmons

Thanks steve. I arrived in the LF scene a little late so i missed out on those View camera issues. I am going to try to get a hold of them. Thanks