Originally posted by ghelary One of the funniest arguments around there. Mpx does matter, if you print. It is true that if you only post on Internet, above 3Mpx it doesn't matter anymore. But on large prints there will be a large difference between say 6Mpx (*ist) and 14Mpx (K7) and 40Mpx (645D) provided everything is shot in similar conditions.
Really? That makes no sense at all... Sure the 40mp picture would be a fair bit larger. After all, that's a tripling of pixels. But going from 6mp to 14mp isn't such a big deal, ESPECIALLY when it comes to printing.
A 6mp picture printed at 300dpi with no scaling whatsoever would be 10" on its long side. At 600dpi, it would be 5" on its long side.
A 14mp picture printed at 300dpi with no scaling whatsoever would be 15" on its long side. At 600dpi, it would be 7.5" on its long side. That's more than double the pixels, and only a 50% increase in size. Or if you want to go the other way, the 6mp picture ends up being only 33% smaller.
If you scaled the 6mp up to the same size as the 14mp picture using high-quality interpolation, the difference would be imperceptible. Both printed pictures would probably look identical. So your assertion that there's a large difference in printing is incorrect. Further improvements in megapixels will also make no difference unless we're talking about doubling or tripling. For example, a 20mp picture would only gain another 5" on the long side at 300dpi, or 2.5" at 600dpi. That's a 33% improvement over 14mp, or the 14mp picture is only 25% smaller. Again, interpolation makes this difference irrelevant. We're already at a point where pixel density on the sensor has come close to its maximum. Doubling of pixels won't be happening again in APS-C or Full Frame.
Someone mentioned cropping, and that's a valid point. Having more megapixels gives us more options for cropping while retaining more detail. We gained a 2.5" to 5" cropping advantage by going from 6mp to 14mp.