You're both right, just the context is different.

Here's oldtimers pov: Consider taking a picture of a star (or any point). If the field of view is equal on both formats, the star/point will need to be smaller on the smaller format. Thus, MF and LF don't need as sharp lenses as 35mm and aps-c. If this wasn't true, if you printed an 8x10 you would have two pictures with different size stars!

Mike


Quote Originally Posted by Lionheart
I'm not so sure about that OS. The cropping effect of the smaller APS sensor actually allows you to get away with a crappy lens because it is at the edges of the lens that the quality of the pro lenses show themselves off. The smaller sensors only capture the center of the image compared to a full frame sensor or 35mm film frame, essentially the "sweet spot" of the lens. That's what accounts for the cropping or magnification factor of the smaller sensors.
Conversely, a full frame sensor will really highlight the edge deficiencies of a lens, even more so than film will show because of the extremely large resolution and quality of these full size sensors. If you're going to splurge on a full frame sensor DSLR, I really believe you need the best lenses you can afford.
Just my two coppers of course, but that's my current understanding of the situation, I could be wrong