I've just read an interesting article over at bobatkins.com about the controversy surrounding the 15MP sensor in the new Canon EOS 50D Camera. There's been a lot of nonsense talked about this new sensor - especially about diffraction. And Bob has succinctly cut through the BS.

So, yes, stopping down past f8 with the EOS 50D might well result in lower image resolution. The important omission is that stopping down an EOS 40D, a Digital Rebel XT, a Nikon D300 or a Nikon D90 past f8 would result in exactly the same thing! Not only that, but the camera with the highest resolution would be sharper at f8. So, for example, the 50D image would be sharper than the 40D image...

...I've even seen some people suggest that images from the 50D will be less sharp than those of the 40D with most lenses. I'm not quite sure of the "logic" they have used in reaching that conclusion, but they got there somehow!

Again these "deductions" are completely wrong. The fact is that the higher resolution of the 50D will result in higher resolution, sharper, images than those from the 40D whatever lens you use. Doesn't matter if it's the pretty average "all plastic kit zoom" shot wide open or a super sharp lens like the EF 135/2.0L shot at f8. The higher resolution sensor of the EOS 50D will result in sharper images in both cases.

You can read the whole thing over at bobatkins.com. And there's some interesting real world proof of this at a blog called Serious Amateur Photography here and here.