Q - diffraction and resolution

Started Feb 15, 2013 | Discussions thread
viking79
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Re: Method
In reply to steephill, Feb 16, 2013

steephill wrote:

Eric,

Same treatment for all - RAW, my standard LR sharpening, 60 amount 1.2 radius, 80 masking and detail left at 25. I checked focus both visuallly and with focus peaking but the same setting used for all shots.

Three shots for each setting to check for variability especially as shutter speeds got very low at smaller apertures. Tripod mount on lens, SR off.

I could see some atmospheric disturbance in some shots but otherwise results were very consistent so I am confident that I am seeing the impact of diffraction.

I also used my mirror lenses, here is what my Tamron 350mm f5.6 could do :-


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Steve
www.pbase.com/steephill

Thanks! I still think conceptually we are seeing something like the following image, where "some other lens" would be something like the 8.5mm f/1.9 or something similar. I have over exaggerated the aberration limited slope. You can't beat diffraction, it is a hard thing and will effect every lens in a similar matter.  Some lenses might do worse than the diffraction limit, but they can't do better.

The Q sensor has very high resolution demands, about 330 lp/mm, where most SLR lenses are lucky to resolve 100. So I guess the images make sense, just my intuition would have thought the prime would be a bit sharper than that from f/4.5-5.6, but again, you don't notice this on a comparatively non-demanding 16 MP SLR like the K-5.

Eric



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