Diffraction and the Mamiya 7 50mm

[evanbaines]

Hi everybody!

First post!

I dearly love my Mamiya 7ii, and am now the proud owner of a brand-spanking-new 50mm lens for her. I have been unable to find any MTF charts for this lens, and was curious as to exactly where diffraction starts to set in... trying to come up with a reasonable guestimate of the sharpness trade-offs in the smaller apertures of diffraction vs. depth-of-field for tripod-mounted landscape shots. Assuming adequate depth of field, where will I maximize resolution, and is f/22 still going to give me a solid resolution if I need it? (understand that I am used to Canon WA lenses that rapidly fall apart past f/16).

Here is a completely unrelated photograph of my lovely wife using the 80mm lens wide open on HP5+, just because I figured I'd include a picture for my first post.

 

[antiquark]

Plug in your numbers into the diffraction calculator at:
http://www.cambridgeincolour.com/tutorials/diffraction-photography.htm

I plugged in a few numbers, and you should be fine up to f/32. An interesting thing you'll notice is that the focal length doesn't affect diffraction, only aperture.

 

[sparrow6224]

Your question strikes me as very funny for, a.) I've just (gasp) won an auction for a Mamiya 7 ($$$$$!!!! ouch) and just tonight was reading the following, which I found intriguing, from Mr. Rockwell (not the one who does the best/worst dressed lists, either).

 

[sparrow6224]

Obviously, I see now, the chart is missing. Just scroll down this page for the whole business, if you're interested:
http://www.kenrockwell.com/mamiya/7.htm
He says he's taking diffraction into account.

 

[oftheherd]

Always good to have detailed formulas worked out ahead of time, and experiment with them for your own use. But with MF and LF, your aperture's actual diameter isn't going to be as small as with with 35mm or non-full frame digital. So the effects aren't going to show up as soon.

 

[StuartR]

I have never had a problem with diffraction on the Mamiya 7 -- film is more forgiving than digital (no pixel wells) on this front, and I have printed huge (1mX1m) from film shot at f/22, and while it might not be as sharp as it would be at f/11 at the point of focus, the overall sharpness of the image is often higher since the sharpness is carried over a wider depth of field. I would say you can shoot without reservation on the Mamiya 7 -- whatever aperture you need for depth of field or shutter speed will give you the optimal results. Any tiny differences in flat field sharpness between apertures is insignificant compared to the benefits of choosing the appropriate aperture for your depth of field and exposure time requirements. That's why you pay the big bucks for a superb 6x7 rangefinder -- you can use it at all settings!

 

[EdSawyer]

I have several scans of magazine tests, including lens tests, on the mamiya 7 at : http://www.edsawyer.com/lenstests/

The 50mm is the best lens in the system overall, by some measures. The best apertures are f/8 and f/11. Beyond that you give up some sharpness. I'd only go smaller (f/16, f/22) if DOF is the priority, but the lens already has great DOF even at f/8.

-Ed

 

[Turtle]

Shoot without reservation and use F22 or beyond only when you must. Its def sharper at F16 than F22. At F11 you will only see the improvement over F16 or so when using slow film and a tripod and printing big.