Nikkor SW65mm f/4 - diffraction and aperture question

[Lee Christopher]

I've searched the forums and other than one thread which seems to have stopped in mid-air, I could not really find anything concrete.

I was wondering what are the upper usable aperture limits of a Nikkor SW 65mm f/4 on a 4x5 view camera? I've seen f/32 causing diffraction (overall lack of sharpness using a 6x12cm format back), but what about f/16 - f/22? I vaguely recall reading somewhere that the sweet spot for this lens is f/8 - f/11, but often, that's still too large for me.

If you were shooting landscapes or interiors, and needed the sharpest results with maximum depth-of-field (after factoring in tilt and swing), what's the smallest aperture you can get away with on this lens?

Thanks in advance.

[Dan Fromm]

How large do you intend to print?

The magic rule of thumb for diffraction limited resolution is that the best possible resolution in lp/mm with a perfect lens is 1500/f#, where f# is the f/number, e.g., 8, 11, 16, ... Understand that this is the best possible with a perfect lens and technique and unbelievably high resolution film and ... You'll never do that well. Also understand that the best possible resolution is a very low contrast.

Now recall that the conventional minimum resolution on paper for a print to look sharp when examined closely is 8 lp/mm. Some will argue for lower, others for higher, but the convention is 8 lp/mm.

So, if you shoot at f/16 and everything is perfect you'll get a bit over 90 lp/mm on film. If everything is perfect, and it won't be. But anyway, as long as we're doing numerical exercises, you won't be able to enlarge more than 11x without getting less than 8 lp/mm on paper. If everything, including your enlarging lens, parallelism between negative and paper, focus, ... is perfect. Which it won't be.

But now you should have the idea and will be able to calculate yourself into oblivion. At the least, you should understand why its a rare 8x10 print from 35 mm film that will stand close scrutiny.

Cheers,

Dan

[Lee Christopher]

Thanks Dan.

I'm looking at several options:

A2 - A1 sized (roughly) or a panel of custom sizes based on the 6x12 film printed up to about 5-7 feet long each.

How much does it matter that the trans or negs would have to be digitized first, and can be sharpened digitally? I generally do not like to over-sharpen in the computer as far as possible.

[Paul Kierstead]

I still fail to see how sacrificing the artistic merit of the photography by using insufficient DoF is superior to having some overall resolution loss due to diffraction. Lack of DoF is much, much more obvious then diffraction. Unless, of course, you decide to forgo the photograph because you cannot achieve the desired DoF without loss due to diffraction.

[Juergen Sattler]

I still fail to see how sacrificing the artistic merit of the photography by using insufficient DoF is superior to having some overall resolution loss due to diffraction. Lack of DoF is much, much more obvious then diffraction. Unless, of course, you decide to forgo the photograph because you cannot achieve the desired DoF without loss due to diffraction.

Amen to that!

[Ed Richards]

For 4x5 and this lens, I do not see diffraction effects in real world shooting at f32. But for 6x12, f22 is pushing it, and f32 probably will show effects.

[GPS]

For 4x5 and this lens, I do not see diffraction effects in real world shooting at f32. But for 6x12, f22 is pushing it, and f32 probably will show effects.

That's not a good example as 6x12 is just slightly cropped 4x5 and you don't enlarge it so differently.

[Ivan J. Eberle]

This question isn't meaningless if you're seeking both high DOF and high resolution-- if you want to create very large gallery prints, for instance. After 30+ years of photography but only a couple of years into MF and LF, I'm still discovering the limits of both, and just starting to getting a sense of which scenes to either walk away from, or pull out the MF camera and put away the LF.

For planar subject matter, LF is king. For scenes having subjects in three dimensions, it's not as clear-cut. The near-far thing that I've been attempting to do with a Nikkor SW90 is sometimes impossible to pull off. The smaller formats have a couple of natural advantages and nowhere is it more evident than DOF with wide angles. (Incidentally, film has a somewhat similar advantage over digital sensors, too.)

[Dan Fromm]

Lee, there's no way that a print 7' long from a negative 120 mm long will pass close scrutiny. None. So, do the prints you intend to make have to pass close scrutiny?

Ed, one of the weaknesses of my macro work is that I shoot at too small effective apertures. When fine details matter effective f/22 is discernably worse than effective f/16. And lets not even think about effective f/32 (f/16 set at 1:1), where I often work.

Ivan, that shooting a lower magnification and then enlarging more will yield more DoF in the final print is just barely true but practically no help at all. Fortunately most of the people who look at our work -- as an amateur I don't have to deal with insane art directors -- are much less critical than we fear they will be.

Cheers,

Dan

I suggest that those of us who don't have a copy of John Williams' book Image Clarity buy a copy and read it. Its the second most frightening book on photographic technique I've read. The most frightening is H. Lou Gibson's Photomacrography.

[Lee Christopher]

Thanks for sharing your thoughts and opinions.

I may have to re-define and manage expectations somewhat differently in light of this information.

I won't sacrifice a shot just because it require f/22 or f/32. I'll still do it and see how it can be improved (or salvaged) later on, or think of different ways to present it.

Best regards.