ND or stop down

[AFSmithphoto]

Does anyone have any thoughts on which will have a greater adverse effect on a photograph, using an ND filter, or stoping down into diffraction limited territory?

I imagine it would depend on the qualty of the filter (Plastic vs glass or single/multi/non-coated.) The ND I happen to have is a non-coated tiffen glass ND9, so I think I'd stop down and save the ND for times I need a REALLY long exposure in bright light, but I thought I'd post the question here to get some feedback on the trade-offs in general.

[christopher walrath]

I would think the less you add to a photograph when addition isn't needed would be better. The filter would provide two additional reflective surfaces wherein glare could have a happy little 'ruined your shot' party between the film and the subject. As pertains to LF, I really couldn't venture as I am a newb but this is just one idea. Food for thought.

[Donald Miller]

It depends on how much you would stop down and how large you plan on enlarging the negative. Diffraction does enter into the consideration at some point.

[Brian Ellis]

If you're talking about a 4x5 negative and stopping down to f64, diffraction isn't really noticeable until you get into big prints, something in the 20x24 range and larger. Diffraction is a significant potential problem with smaller formats, especially 35mm, because of the big magnification factor involved. For example, an 8x10 print from a 35mm negative is about an 8x enlargement factor on the long side, approximately equivalent to a 32x40 print from a 4x5 negative (which is why most 35mm lens don't stop down below f22, sometimes only f16). I don't really think either a ND filter or stopping way down will have a noticeable adverse effect on a 4x5 negative and a print in the 16x20 or smaller range, assuming a good quality filter and a situation where glare isn't a problem.

[anchored]

Assuming you are using high quality filters, and being careful to shade them from errant flaring, and if they are clean, there should be no detrimental impact to an image... including for large prints (over 20"x24"). Personally I would prefer to employ ND's whenever needed to adjust shutter speeds down while maintaining specific aperture settings.

[vinny]

Conduct a test by shooting with your lenses at various apertures including 45,64, and 90. Then those results will convince you to USE A FILTER! Most, but not all, folks that say just "stop in down", haven't made prints from those negs comparing them to the optimal aperture of the given lens. Or they haven't got a sharp print to compare it to. I'm not saying Brian hasn't tested his lenses.

[vinny]

should have read "stop it down"

[Brian Ellis]

Conduct a test by shooting with your lenses at various apertures including 45,64, and 90. Then those results will convince you to USE A FILTER! Most, but not all, folks that say just "stop in down", haven't made prints from those negs comparing them to the optimal aperture of the given lens. Or they haven't got a sharp print to compare it to. I'm not saying Brian hasn't tested his lenses.

Vinny - Actually I haven't "tested my lenses" to determine their "optimal aperture." I only pay attention to getting the depth of field that I need in any given photograph and use whatever aperture is necessary to accomplish that (using the method described by Paul Hansma (sp?) in his Photo Techniques article many years ago and I believe also described in Tuan's article on this site except that I use the Linhof tables rather than Hansma's tables). I don't care whether that's the tested "optimum aperture" for any particular lens or not since the detrimental effects of inadequate depth of field will IMHO be much more noticeable than the effects of diffraction.

While I haven't tested my lenses to determine their optimal aperture, what I have done on several different occasions is make three photographs of the same scene at f22, 45, and 64 to determine whether I could see any difference in "sharpness" or anything else among them. I've never been able to see any difference except with a series of darkroom prints I made years ago when I was printing at the equivalent of roughly 20x24. At that size I could see a very very small difference between f64 and the smaller apertures but even there I don't think I or anyone else would have really noticed any excessive softness except with the comparison prints available.

I noticed that you didn't qualify your message by the size of the print, which makes me a little dubious about your statement because I think it's uniformly agreed that print size is very relevant in determining the effects of diffraction. OTOH, maybe your eyes are better than mine (which I don't say sarcastically, my eye-sight isn't all that great) or maybe other factors such as viewing light or the type of subject matter of my test prints and yours or other things are coming into play. But I feel comfortable for my own work in saying that diffraction isn't noticeable at f64 with a 4x5 or larger negative and a print in the 20x24 range or smaller. Others can do their own tests and see what they think.