Strange Question

Kevin Kehler · Feb 8, 2010

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?

Ian Grant · Feb 8, 2010

Most LF lenses for 5x4 are optimised for f16 to f22 and that's when you get best resolution.

Ian

Kevin Kehler · Feb 8, 2010

Thanks Ian, I figured as much but thought I would ask.

Changeling1 · Feb 8, 2010

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.

Bruce Watson · Feb 8, 2010

Kevin Kehler said:
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.

Ian Grant · Feb 8, 2010

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

Vaughn · Feb 8, 2010

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

Ed Sukach · Feb 9, 2010

Ian Grant said:
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.

JBrunner · Feb 9, 2010

Almost any lens has a sweet spot, but in practice modern lenses perform so well that aperture usually isn't the weakest link IME.

Chuck_P · Feb 9, 2010

Ian Grant said:
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.

Mark Sawyer · Feb 12, 2010

When I bought my 480mm Apo-Ronar, I made an exposure stopped down to f/256, just because I'd never had a lens that shut down that far. The negative contact printed very nicely, with more resolution than I could see with a loupe. And it's worth noting that Edward Weston made some of his most famous still-lifes through a pinhole aperture inserted into a lens.

If you enlarge considerably from a fine grain film, you might have issues. Since I only contact print, I never worry about closing down "too far".

Of course, now that I work more with soft lenses, I tend to stay close to wide open...

Ian Grant · Feb 12, 2010

Mark's right, I come from the other side I ONLY enlarge, but these small apertures haven't caused a drop in resolution yet

I try to stay one stop off the minimum aperture and that seems to work well.

Ian

jdimichele · Feb 27, 2010

While it is true that most lenses that are not optimized to be shot wide open (ie: fast telephoto lenses), don't let this get in the way of your photographic vision. One of the reasons shooting wide open (or close to wide open) in large format is a very narrow depth of field. Since a large portion of your image is going to be soft/out of focus, the lens shortcomings won't be as noticeable. On the other end of the coin, if you shoot with the lens stopped all the way down, while there may be some diffraction present, the fact that most people probably don't enlarge their 4x5 shots much passed 16x20 which is only a 4x enlargement factor. Keeping in mind that most technical issues of a photo are more visible the larger the magnification factor. Therefore, shooting at f45 on 4x5 is not as much of an issue as shooting 35mm at f22.

Cheers,
Jay
www.jasondimichele.com

Mike1234 · Feb 28, 2010

Gains from stopping down a lens are "mostly" off center and are greatest at the farthest corners and using movements increases the need to stop down. There are a few exceptions. For instance the Kodak 203mm Ektar dialyte is usually sharpest wide open at f/7.7 but doesn't degrade much, if any, stopped down to f/16 or so. Portraits can often benefit from wide-open distortions if the center of interest is... centered

John Koehrer · Feb 28, 2010

Mark Sawyer said:
And it's worth noting that Edward Weston made some of his most famous still-lifes through a pinhole aperture inserted into a lens.

...

I'd never heard that one before. Where did it come from?

jbbooks · Feb 28, 2010

Light fall off is an issue with some lenses and stopping down helps. When using a graduated neutral density filter (a center filter) to control fall off, stopping down is necessary to obtain the full benefit of the filter. As to corner sharpness, stopping down can improve the resolution and can help with any off-center imaging (using movements).

A partially vignetted, swirly image may be just the thing for you, but, if it is not, stopping down will eliminate a lot, if not all, of it. Generally, unless there is some desired effect that requires opening the aperture, stopping down to at least the middle of the range available will be worthwhile. And, as has been said, the benefits of stopping down even further usually outweigh any concerns about diffraction.

Mike1234 · Feb 28, 2010

I'll post my reply another way...

Will the loss of detail (usually off-center) plus limited DOF help or hinder "your view" of the final print? It's a decision based on lens performance and artistic expression... subject, lens, photographer's vision, final print, etc. As AA would put it, "the it's the neg's score vs. the print's performance". Write the score (neg) to achieve the final performance (print) you envision for the subject. No one here can help you with that because only "you" can. We do not have "your vision" of "your subject".

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