Thread: Diffraction. When does it really matter with LF?

1. Re: Diffraction. When does it really matter with LF?

Jim's post reminds me of a little trick I learned from ancient markings on a couple of my old shutters: put little paint/pencil marks on the aperture scale at 1 inch and 1 centimeter. It makes the bellows extension math incredibly simple. 30 cm extension at 1 cm aperture? f/30. 45cm extension at the same aperture? f/45.

For a smaller apertures, a mark for .5 cm is almost as simple.

2. Re: Diffraction. When does it really matter with LF?

Originally Posted by Mark Sawyer
For large format, this is key. If you're contact printing, (no enlargement of the negative), forget diffraction. It will barely show up at f/256.

Nitpicking, but isn't 1:1 and f/16 nominal really f/32 effective?
They are from a light exposure point of view, because light obeys the inverse square law , but does that mean that diffraction, which does not rely on the inverse square law, is the same at 1:1 and f/16 is the same as infinity and f/32. My gut tells me not.

3. Re: Diffraction. When does it really matter with LF?

For me, depth of field trumps diffraction degradation every time.

I shoot 4x5. If I have to stop down a lot, I just reduce the maximum enlargement size I can get from that particular negative. Printing 8x10 from 4x5 film, I can stop way down, even to f/64, and not get objectionable diffraction degradation.

Also, it seems that scenes that need a lot of stopping down are the ones I don't want to enlarge much anyway; things like close-up still lifes, natural details, etc.

One of the big advantages of large format is that one can use movements to optimally position the plane of sharp focus in a scene and thereby be able to use a smaller aperture than one would need without movements to get everything acceptably sharp. Mastering view-camera technique is a real help.

Best,

Doremus

4. Re: Diffraction. When does it really matter with LF?

Originally Posted by cowanw
They are from a light exposure point of view, because light obeys the inverse square law , but does that mean that diffraction, which does not rely on the inverse square law, is the same at 1:1 and f/16 is the same as infinity and f/32. My gut tells me not.
Bryan, your gut is mistaken. See, for example, H. Lou Gibson's Close-Up Photography and Photomacrography, EKCo publication #N-16.

5. Re: Diffraction. When does it really matter with LF?

The nearest library copy is the centre of Canada, that is Toronto. One day I will get there

6. Re: Diffraction. When does it really matter with LF?

Originally Posted by cowanw
The nearest library copy is the centre of Canada, that is Toronto. One day I will get there
Inexpensive at on-line used book stores.

7. Re: Diffraction. When does it really matter with LF?

In the late 1970s and early 1980s I shot a lot of waterfalls in New England with my 8x10 and a 12" Wollensak Velostigmat Series II. All exposures shot at f/64 or f/90. At the time I made contact prints on Varigram or Varilour FB paper. Around 10 years ago scanned the negatives and made digital negatives to print Platinum/Palladium prints from. Loss of sharpness from diffraction is definitely in the original 8x10 negatives if you look at them under a low power X4 Loupe. Holding the prints side by side at arm's length, most people would say, resolution wise, that the FB prints are a tad bit sharper than the Platinum/Palladium prints. Aesthetically and tonality wise, the Platinum/Palladium prints far outshine the FB prints. Several of my friends/relatives are not photographers and when asked which print is sharper, all responded that the Platinum/Palladium print was definitely sharper. When I am doing Photomicrography or Photomacrography diffraction, to me, is a major concern and factor. When I am shooting outside with my 8x10 or 11x14, diffraction matters little to me. The image matters all to me. If I were concerned with loss of sharpness from diffraction, I just might never take out my 8x10 and 11x14 ultraWA pinhole cameras. To me the final image in the final print is what matters the most...

8. Re: Diffraction. When does it really matter with LF?

Re Greg's post #17 above, +1. Sharpness is overrated.

9. Re: Diffraction. When does it really matter with LF?

From my own practical needs, I try not to go smaller than f/32 for 4x5 format, or smaller than f/64 with 8X10 film (or smaller than f/45 if a large print like 30X40 inch is in mind). Obviously, I'm referring to enlargements; I rarely contact print.

10. Re: Diffraction. When does it really matter with LF?

Hi all,

So, I've re-read the thread and here's what I was able to get out of it....

- There are rules of thumb to determine diffraction
- There are generalities that guide users with how to avoid diffraction
- There a school of thought that goes something like this...'so what, just shoot more'
- There a school of thought that understands the compromises involved in photography so pick the one that most important to you at the time of the shot
- Large format affords the user unparalleled flexibility to minimize diffraction, take advantage of it

Pretty good, I can roll with that.

Thanks!!