Time for a bit of text musing. Yesterday Canon announced the 15.1 mp 50D, 1.6 crop sensor and today Nikon announced their D90, though with the same pixeldensity as the D300. Now.. both great cameras, and i dont care what it says on my camera as i shoot with whatever i can get my hands on.

But there is something called diffraction blur which basically means that the more megapixels you put on the sensor without increasing the actual size of it, the more trouble you will have with the optical side of your system, the lenses. This is then seen in the higher apertures where you have significant degradation of finer detail in an image. Yes, so when you would assume you would get more sharpness due to a higher aperture value, you actually get less.

Here you can see a direct example of this on a full format sensor (the Canon EOS 1Ds mk3) : http://www.openphotographyforums.com/forums/showthread.php?p=46107#post46107

So, back to the new cameras. The full format sensor shows this at around 20-25 MP to an degree where it’s a real problem. As many have stated shooting above F5.6 is going to ruin the fine detail quite a lot. Not fun for those of us regularely shooting at F8-F11 and even up to F32 in some extreme cases.

And remember, this is full format. When you look at a 1.6 crop sensor (like the 50D ) the effect should be visible a lot earlier (on oh.. about 15 MP perhaps? =) due to the smaller sensor size compared to the pixeldensity.

So are we hitting the wall with the MP race now? Not in terms of technical prowess off putting more pixels in a sensor, but the fact that you will need to create much better optics (and thus more expensive) to match?

Well, i dont know. I’m a little worried as im about to invest in a full format system on the small-frame range and awaiting Canons next full format system to be announced. But if they are cramming in a 20+ mp sensor on a full format it would mean i would have to invest in a lot better lenses than i have now (and i use L lenses in the canon range already).

That cost will bring me into digital medium format very fast indeed. Since with MF the physical size of the sensor is much larger, the problems with diffraction comes at a much higher MP level.

It was much easier with film :D