Quote Originally Posted by wickerprints


A 24x36mm "full frame" sensor is 1.6 times larger in linear dimension than a 22.3x14.9mm APS-C sensor. In terms of sensor area, the full frame has 1.6 * 1.6 = 2.56 times the area of the APS-C sensor.


Since pixel count is based on the area of a sensor and not its linear width/height, the appropriate math is


21 MP / 2.56 = 8.2 MP,


so Daniel quoted the correct value.
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Ah OK that makes sense, thanks . Also I checked the specs of the 30D and of course both you and Daniel are right about the pixel density being the same. Which surprises me - why didn't we have a 21MP full-frame sensor in the days of the 30D if the technology was there?? [:S] I guess it's not all about pixel density but also about processing large images quickly as well as storing them. It's an interesting point though - it means there is more to the idea of crop sensors giving greater reach than some people claim.


Daniel - thanks for your explanations too, I see what you're getting at. But if we then take the 7D as an example, with its considerably higher pixel density, then I take it that the gap between cropping and extenders is at least narrowed?