I have to say though, I've read quite a lot that agrees with my opinion that DX sensors are harder on lenses than full frame sensors.
Gavin, it depends on what you are talking about and on which part of the whole digital imaging process you are referring to.
As for resolution (say, levelled in pair of lines per mm resolution power) yes a "full frame" sensor will be "gentler" on lenses than a "DX" sensor
if and only if those two sensors have the same megapixels number.
A "FX" or "FF" 24x36 12MP sensor will be less hard on lenses as for resolution (thus, as for the lenses sharpness) than what a "DX"17x24 12MP sensor will be because the "DX" 12MP sensor is, finally, the "center crop" of a virtual "FF" 24MP sensor. Get it ?
But how do you compare a 24x36 12MP sensor to a 17x24 8MP or 10MP sensor while using the same lens at the same aperture and in front of the same subject evenly illuminated by the very same light ?
😉
And then, resolution is not all.
Chromatic dispersion (that pesky CA & purple fringing problem) in particular is an important factor for an image not to appear sharp and full of crisp details.
In that matter, "FF" sensors are a problem in particular when used with old lenses designed for films.
The best lens sales for the 5D were for the 24-105 that was released specially by Canon for that body.
The 17-40 L which was a killer with film is just above average with the 5D, OTOH it's a killer once and again in front of the 20D/30D/350D sensors.
Yet an old lens can produce terrific images in front of a sensor once you accept to spend several hours tweaking the digital file with a RAW software and another software suite so that all the problems are corrected.
This is called the lightroom post-processing.
This is mainly what people ready to spend $2500-$4500 on some high-end prosumer digital ecuipment have the greatest difficulties with : I mean, people actually don't want to acknowledge that the image isn't completed in the ultimate way just a few seconds after the shutter button was depressed.
:angel: