Yup..... was going to edit my post but to make myself clear "irreparable damage to the processed tiff file" was what I should have said. In any case don't ever use that so called feature.
Victor
Have you actually tested this feature or are you basing your statement on the fact that no dedicated sharpening program can do it? And if so, what was not satisfactory and is it usable in certain situations?
I'm a bit too fuzzy in the brain after a long week to recall my optics classes in college, but I wouldn't rule it impossible to do. Since diffraction is basically a scattering of light it might be possible to undo up to a point (pun intended too). I'm just not that convinced about it being possible at all without measuring the diffraction on each lens and shutter combo, and perhaps even include the sensor (maybe by shooting an image at the optimum aperture too and use that kind of like LCC?)
If the software could recognize the diffraction patterns in an image by itself surely that would take a lot more calculations than the speed at which C1 Pro 10 applies this sharpening would suggest. It's even less likely that they could do it perfectly on the first try, since diffraction also affects color, and not boast about it more, since they would then have literally reversed a law of pysics.
Edit: Now that I come to think of it, if it were possible to undo diffraction there would be no need to focus a camera anymore either or close down your lens or even buy a sharp lens in the first place. Most of the practical problems photographers face are diffraction related.