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Strange Question
I have been taught that lenses need to be stopped down 2-stops in order to have less "issues" (like distortion, softness, light fall off) with them. Thus, while you might have a F/2.8 lens, it will perform best (a very subjective term, I know) at F/5.6 or F/8. While I do like shooting at F/8, I don't slavishly adhere to this rule (all else being equal, it is a good way to get a nice DOF without worrying about diffraction). Since most of what I shoot is not moving (architecture), I need not worry about shutter speed as much as if I was shooting sports.
However, I look at a large format lens like a Nikon 150 F/8 and it is already at F/8. Does this mean it needs to be stopped down to F/11 or F/16 to avoid issues like distortion, light fall off and corner sharpness? Or is the larger glass naturally going to avoid these types of issues?
Once a photographer is convinced that the camera can lie and that, strictly speaking, the vast majority of photographs are "camera lies," inasmuch as they tell only part of a story or tell it in a distorted form, half the battle is won. Once he has conceded that photography is not a "naturalistic" medium of rendition and that striving for "naturalism" in a photograph is futile, he can turn his attention to using a camera to make more effective pictures.
Andreas Feininger
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Most LF lenses for 5x4 are optimised for f16 to f22 and that's when you get best resolution.
Ian
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Thanks Ian, I figured as much but thought I would ask.
Once a photographer is convinced that the camera can lie and that, strictly speaking, the vast majority of photographs are "camera lies," inasmuch as they tell only part of a story or tell it in a distorted form, half the battle is won. Once he has conceded that photography is not a "naturalistic" medium of rendition and that striving for "naturalism" in a photograph is futile, he can turn his attention to using a camera to make more effective pictures.
Andreas Feininger
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Well for starters, if you're shooting mostly architecture you will find a large format camera with full movements to be absolutely indispensable. Without the perspective control of a large format camera architectural photographs are nearly useless. You could put together a 4x5 starter kit for about $300.00 or less and produce photographs that will blow the doors off 35mm and 120 roll film cameras. With a large format camera you will be using very small f-stops on the order of f/32 and f/45. If buildings are your passion you might just as well start out using the best tools for the job.
"A certain amount of contempt for the material employed to express an idea is indispensable to the purest realization of this idea." Man Ray
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 Originally Posted by Kevin Kehler  However, I look at a large format lens like a Nikon 150 F/8 and it is already at F/8. Does this mean it needs to be stopped down to F/11 or F/16 to avoid issues like distortion, light fall off and corner sharpness? Or is the larger glass naturally going to avoid these types of issues? Nope. Stopping down helps just about any lens. What you are doing in stopping down is using more of the center glass by shading out the glass on the outer edge with the diaphragm.
As a previous poster said, most LF lenses are optimized for f/16-f/22. That's not to say you can't shoot at larger or smaller openings. But max resolution will often occur at f/16 or f/22.
Distortion is typically controlled in lens design and isn't much effected by aperture. Same for light fall off. Corner sharpness isn't much an issue with modern lenses, but with older lenses stopping down does help with corner sharpness.
What stopping down really helps with are the aberrations. Things like spherical aberration, chromatic aberration, coma, etc.
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Someone posted a thread somewhere with stats on the apertures John Sexton has used most in his published images (where he gives data) and that blows a hole in the myth that LF lenses shouldn't be used stopped almost right down because of diffraction.
It's about getting the balance right and knowing what a lens does in practice rather than on an optical test bench.
Ian
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Agreed Ian -- I use f64 to f90 probably 90% of the time (tho I just contact print), due to the complexity of my forest scenes. I need that dof!
vaughn
At least with LF landscape, a bad day of photography can be a good day of exercise.
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Originally Posted by Ian Grant Someone posted a thread somewhere with stats on the apertures John Sexton has used most in his published images (where he gives data) and that blows a hole in the myth that LF lenses shouldn't be used stopped almost right down because of diffraction.
It's about getting the balance right and knowing what a lens does in practice rather than on an optical test bench.
Ian Absolutely!!! Finally ... a light ... a bright light - through all this "darkness".
If the quality of a lens - any lens - from a reputable manufacturer was degraded significantly, or even marginally, by the use of ANY "stop", that stop would NOT be there.
Carpe erratum!!
Ed Sukach, FFP.
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Almost any lens has a sweet spot, but in practice modern lenses perform so well that aperture usually isn't the weakest link IME.
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Originally Posted by Ian Grant Someone posted a thread somewhere with stats on the apertures John Sexton has used most in his published images (where he gives data) and that blows a hole in the myth that LF lenses shouldn't be used stopped almost right down because of diffraction.
It's about getting the balance right and knowing what a lens does in practice rather than on an optical test bench.
Ian Seems most were f32 and smaller---------I think.
Flickr
"I find it always necessary to stress that we cannot equate brilliance with contrast."
---AA ( The Print)
".....in printing we are trying to breathe expressive life into the image,.....this raises intangible issues that do not yield to formulas or measurement."
---AA ( The Print)
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