Originally posted by philbaum Here's a diffraction quote i posted here in Jan 2009:
Diffraction Article by Lloyd Chambers
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The Jan/Feb 2009 issue of Photo Techniques, Photo Techniques Magazine - The Magazine dedicated to professional photographers, has an excellent article on: Diffraction: Resolution Taxed to its Limits
The author explains:
Notice that the table above is all about pixel size. As i remember the article from 18 months back, the problem with small photosite size is that as the airy disc gets larger and overlaps half way onto a photosite, its causing a flare like effect that washes out contrast and resolution, in that order. Doesn't matter whether one has downsized to 10 meg from 16 meg, the photosite size is still the same. (i think - this is far too complicated for me to be sure about it)
Optical Sensor technology has moved on since that January 2009 article, which itself was based on limitations of even older sensor designs (i.e. cameras already in the market)
Take a look at the High-ISO performance of the latest K-R/K-5/D7000 cameras, and you can see that in action.
Sensor technology ultimately cannot break pass the laws of physics, of course, but the limits of what's currently possible are constantly being broken.
I cannot say often enough - Diffraction is an optical effect caused by the lens aperture specifically, accentuated by possibly other lens flaws.
All that happens on the sensor is that as sensor resolution gets higher and higher, those flaws, including diffraction get more visible.
Sure, were going to hit a limit with APS-C sized sensors soon, I think, because lens performance has not improved to the same extent.
I have a few El Cheapo old lenses which were OK on my 6MP K100D, rarely used on the 14MP K-7, and I think I will either throw them away or sell cheap on E-Bay when I move to the K-5.
For most users, my advise is - get a better quality lens.
Some lenses which were reasonably OK on the K10D may likely not cut it on the K-5.