Diffraction Test - Phase P40+

[Ebe]

Diffraction Test:

Phase One P40+ with Mamiya 120D Macro & Mamiya 150D

Full view to show where 100% cropping occured.
100% crops, marked with f-stop
Sharpening and NR unchanged betwen pictures.
Heavy tripod, miror lockup, self-timer, focus locked.

f/8, Excellent detail
f/11, The difference is extremely minimal
f/16, Slight loss of detail. Images are not quite as crisp.
f/22, Starting to go soft. Crispness is reduced significantly.

 

[Ebe]

Part Two, with the 150D

 

[dougpeterson]

Similar to what we found with the P45+ and the 120mm.

http://www.captureintegration.com/tests/phase-one/

This is an important test because the effects of diffraction are manifested differently for every lens/sensor combo.

Doug Peterson (e-mail Me)
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[Mike M]

Thanks for posting the test.

The amount of diffraction that a person chooses to live with might be a matter of opinion. And the amount of diffraction that a person can recognize visually varies between individuals. A lot of people haven't built much ability to see tiny differences in accutance. I've found that my personal tolerance level for diffraction will actually vary depending on focus distance too. For example, I may find F11 acceptable when shooting objects in the studio at close-moderate focus distances while at the same time finding F11 unacceptable for objects focused at infinity (in which case I might prefer not to stop down passed f8) Just some thoughts.

 

[Ebe]

Mike;

You are correct, it depends on many factors.
The size of final output and viewing distance are critical.
This is 100% pixel peeping, not necessarily reality in print.
Many photographers would find f/16's additional DOF more important than
the small loss due to diffraction. In fact I have shot many pictures at f/16 with the P30.
With the p40+ I have backed off 1 stop. F/11 with the 120D-Macro and the 150D, Other test have proved to my satisfaction that f/8 is the sweet spot for the macro and 5.6 for the 150D. Most of the other prime lens perform extremely well between f/5.6 and f/9.5

 

[Jan Brittenson]

I think this illustrates that it almost never makes sense not to stop down for adequate DoF. Simply stop down and live with the diffraction. Having said that though, this is the back of my Mamiya 7. The left column is the aperture as read on the lens scales for DoF, the right column diffraction-adjusted peak optical performance. Turns out it works out exactly the same for all lenses. This is useful for the case where DoF is easily achieved and the question is how far to stop down - where there are no further gains due to diffraction.

Here's a similar scale I created for my field camera (A45II), fitting over the focusing knob:

In this case the scale is rotated to a zero position at the far (or near) end, focus moved moved to the other end, the scale read, the knob rotated to the center of the distance, and the aperture set to the read value. Works like a charm for Apo-Sironar-S lenses. (No empiricial experience with anything else, but theoretically it should be good.)

Now this is for film, but I'd like to know how it translates to a digital back. Obviously the back adds complexities like a color mosaic (which gets demosaicied using all sorts of heuristics), gaps between sites (where diffraction energy might get 'lost'), microlenses/angle of incidence, etc.