f64

[Jim Jones]

I agree with Drew. A rule of thumb for normal focal length lenses, regardless of format, is: for optimum sharpness, stop down so the aperture appears to have about a 1/4" or 1/5" diameter when viewed through the front of the lens. This gives a good balance between lens aberrations, DOF, and diffraction for many subjects. Long before digital calculators I went through the math for many lenses on several formats with pen, paper, and Rudolf Kinglsake's old Lenses in Photography. It was an education that many of us would find worth the effort. A calculator or computer can simplify the calculations. St. Ansel had good reasons to use f/64, and Weston could get by with smaller apertures with some of his subjects.

[Steve M Hostetter]

Obsession: The domination of one's thoughts or feelings by a persistent idea,image,desire,etc.

[Drew Wiley]

Steve - no obsession. Very practical. Although the ultimate performance of all lenses
us diffraction limited, we must frequently make wise decisions how to use this information. Sometimes f/64 is needed to make a certain lens cover the format
with movements. For example, I know exactly where this tradeoff occurs with a
250 G-Claron with my 8x10. You've only got so much room, and I know that at f/64
nobody will notice the slight degree of detail loss in a 16x20 or 20x24 print, but that
it start to be an issue in a bigger Cibachrome color print, for example. I know that if
I don't need as much depth of field or movement, I'll get better sharpness at f/32.
More often I work with longer lenses like 360 or 450, which have far more coverage
but obviously less depth of field. Today I'll be out with my completely rebuilt old
Sinar 4X5 testing each little repair, so the lens issues will be different, but by now I
know the parameters instinctively and don't even need to think about them. I'll just
know which f-stop works best.

[Brian K]

I've done extensive testing of nearly all of my lenses, using a stereomicroscope and I can state with complete confidence that there will be significant differences in sharpness between a LF lens shot at f 16 or 22 and say f45 or 64.

This difference didn't even require specific testing as it was very noticeable from my days as a still life photographer when I would most often shoot at f32 or 45 to get sufficient DOF and then on the rare occasions where I'd have to shoot at f64.

While an image shot at f64 will appear in focus and sharp given no point of comparison, once it's compared to an f 16 or f22 exposure of the same scene the differences are extremely noticeable under modest magnification.

[Armin Seeholzer]

occurs with a 250 G-Claron with my 8x10.

I did not know this lens does exist, I only have a 240 mm G-Glaron!
But only bootles get sharper at f 64 and f 90!
But if f 64 is needed I take it without any hesitation!

Cheers Armin

[Lenny Eiger]

To all those people trying to explain to me that diffraction is a fact, and try and school me on how to use swings and tilts, please stop. I am not an amateur, I've taught college courses in how to use large format cameras and I don't need the lessons. It only serves to annoy.

I was very careful to say that it proves it to me - and if its only to me, that's fine. FWIW, I think the bottleneck in the amount of sharpness is at the printer. I am also not shooting tabletop or other objects that require that kind of look. While some of you may prefer critical sharpness over DOF, I prefer DOF. This is an aesthetic choice.

What I see is that I have a lightning bolt clearly outlined on a very small droplet of water. I doubt that level of detail is going to make it thru the printer, it might be fun if it does - that's tomorrow's task. I am actually comparing 8x10 to 4x5 and 6x7, to see exactly what one can get and one can't on the same shot, with a perfectly exposed and developed neg.

FWIW, I just compared the 6x7 and there is simply no difference in the sharpness between 11 and 22 when viewing on photoshop at 100%.

I think the Rodenstock Apo S is a great lens. It has superb glass and an advanced coating. All I'm saying is that I am happy with the sharpness all the way down. No one has to follow me if they don't want to.

Lenny

[Policar]

I saw some very impressive 10x enlargements from 4x5 that were shot at f45. The photographer remarked that keeping everything in focus matters psychologically a lot more than having fine detail up close.

f64 isn't too bad on 8x10. Kind of equivalent (in terms of dof and diffraction) to f32 on 4x5, f16 on 6x7, or f8 on 135, I guess?

I'd be curious how f64 on 8x10 compares with f32 (at equivalent FOV) on 4x5 and how that compares with full frame digital.

[Nathan Potter]

The subject matter really determines the aperture I use and in combination with the degree of swing or tilt that I need to compose the image. And indeed I'll sacrifice resolution in the instances where I need overall DOF that can't be obtained by camera movements. Sometimes I'm disappointed with the results from a small aperture when trying to make a substantial enlargement so I just abandon the attempt and print to a smaller format. It is useful to have a feel for the degree of image degradation due to diffraction but the clearest guide is to do the simple calculation. I think in Lennys example he is just trying to get a feel for what an F/64 aperture will deliver with his combination. And yes, a comparison, at high mag., of say f/5.6 to f/64 with his dandy scanner would be most interesting. So Lenny, when you don't have anything else to do , go to it.

Nate Potter, Austin TX.

[Bill_1856]

The blowup looks pretty darned fuzzy to me.

[Lenny Eiger]

The blowup looks pretty darned fuzzy to me.

Well, you don't know what you're looking at. Maybe it doesn't translate on the web. However, I see tons of scans from lots of different photographers. Most are quite sharp. Very few of them look anywhere close to this good. When you blow things up on the computer you have to take into account the viewing percentage. There is nothing that looks perfectly great up at 100% - unless you are familiar with what you are looking at.

So far people have not quite understood what was being presented, others just thought they would re-iterate their positions and others thought I needed to be schooled. I say never mind. We can delete the thread. I'm tired of everyone being crabby, bitchy and egotistical.

Lenny