Originally posted by kytra That is not correct, because by cropping an already taken image one loose resolution (is like digital zoom) as oposed to the "optical" cropping in the case of crop sensors.
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FF camera often have nearly the same pixel density than APS-C sensors (D700 being a notable exception).
Let's take the 5d mkII (3753x5634 for a 24.0 mm x 36.0 mm sensor) : if you crop the resulting 21MP pic to the 15.8 mm x 23.6 mm APS-C equivalent sensor size, you end up with (counting on fingers) 2470x3693 pixels (9.1MP), which is quite plenty enough...
Okay, it's a little bit less than a K10, but I'd trade in a blink anyway...
EDIT: And before someone gives the "bigger aperture" advantage for APS-C, let's consider that a f/2.8 200mm on APS-C is equivalent to a f/4.5 300mm on FF, DOF and FOV wise... And given that FF has better high-iso, the 1.5Ev light loss due to the smaller aperture is easily matched by the better high-iso handling.
So, identical photos can be taken with about the same price tag for lenses... The DA*200 is not that far below the DA*300 price, and you still end up with a slightly better 300mm with the FF solution...
Well, this leaves the body price discrepancy to explain to your wife...