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I'm not sure where you saw that... I suppose time will tell.
In general, though, lens resolution becomes progressively more important as the frame size is reduced. An easy way to think about this - as the camera gets smaller, so do the line pairs you need to distinguish - everything gets tinier.
So, a lens that needs to cover a 120 frame 56mm across with 2,400 lines - resolve 43 lines/mm - would need to resolve the 2,400 lines across 24 mm (35mm frame) instead, or 100 lines/mm with 35mm. This is why the obsession with resolution numbers is largely a 35mm phenomenon.
*actually, if looking at 645, the short dimension is 45mm - so the mf film lens needs 53 lines/mm, to make this a fair comparison to 35mm. But then, APS-C size sensor is yet smaller... though will the digital 645 sensor be larger than a 35mm full frame?
The Pentax APS-C has a short dimension of 15.6mm, so in the above example the lens needs to resolve 154 lines/mm.
Looks like 645D has a short dimension of 36mm, so in the above example the lens needs to resolve 67 lpmm.
Therefore I expect existing 645 lenses to be sharp enough optically, though what other issues there may be with sensors instead of film (angles of acceptance etc) who knows?
ps. I picked 100 lpmm for 35mm because of an old article in Modern Photo, where they were attempting to see if 35mm lenses could achieve medium format quality on film. A few lenses did manage that, with the best films available at the time.
Last edited by Nesster; 03-03-2010 at 10:11 AM.
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