« on: February 12, 2014, 03:05:37 AM »
This is the diffraction myth. Diffraction is diffraction, it is the same regardless of the sensor. The difference in pixel size simply means your imaging the lesser effects of diffraction sooner, but that does not make the effect worse. Diffraction is purely optical, so whether you are using a FF sensor, an APS-C sensor, or a small 4/3rds sensor with even tinier pixels, you should really NEVER worry about diffraction.
So, technically speaking, stopping down to f/11 is stopping down to f/11...the ultimate result on IQ in reach-limmited scenarios (same lens, different cameras, same subject distance) is roughly the same regardless of FF vs. APS-C (technically, APS-C would actually have the edge, barring blurring from other factors...i.e. the 7D has a stronger low pass filter than the 5D III, which mitigates some of the benefit of having smaller pixels, but not entirely.) Smaller pixels will always give you a cropping advantage, and the more you stop down, the returns offered by those smaller pixels simply diminish until they offer no benefit over larger pixels (but at no point would smaller pixel EVER be "worse" than larger pixels from the standpoint of diffraction...noise is another matter.)
Thanks for the link. Pretty good points.
I ran across this post by Roger Cicala at lensrentals blog. He comes up with roughly similar findings using narrow apertures on a D800 -