A non Sigma photographer I know 22mp is supposed to be the threshold where digital will rival 35mm full frame film. Which if this is the case the SD1, D3s, D3x and the various 25mp Canons already exceed the resolution of film.
The one set of premium scans I had done at Richard Photo Lab in Hollywood are of 35mm film and the resolution is 16.8 mpixel. That's the most they offer.
Based on the relative size vs the SD1 APS-C sensor, the SD1 has more resolution, hence the issue regarding lens limitations. Certainly it's better than any scan I can get of film, unless I buy my own high-end film scanner (which I won't be doing).
However, the sensors in other cameras are Bayer sensors, and even though the Canon 5DII has 21 mpixels film is still better. This is because each pixel on a scan of film is a full-color pixel and each pixel in the Canon/Nikon/etc is a single color pixel (pick your color). My guess is that a full-frame Bayer sensor to match film would have at least 40 mpixels, but a Foveon full-frame sensor would only need about 18 mpixels. And, the Foveon pixels in such a sensor could be made bigger than they are in the SD1!
Still, the full-frame Canons and Sonys make a nice picture, better than all but the finest professional films in my opinion. The top of the line films and the top of the line processing and scanning will still show film beating them. Probably not beating the SD1 though.
And, film has its own unique character, different from all digital images but getting harder and harder to see as digital progress marches on.
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Tom Schum