Quality of digital photographs are determined by four major factors:
1. image sensor size and quality
2. lens optics
4. processing core
These are placed in order of importance. Yea, image sensors and lens optics are that important.
I have never seen a good illustration comparing the basic image sensors so I put one together. There’s also a 300 dpi illustration on my flickr page.
I was shocked to see how much smaller Canon’s “full frame” (C) is than Nikon’s full frame (B). Hooray for Nikon. Canon’s “full frame” can be considered to be simply a half way point between Nikon’s standard SLR sensor (D) and Nikon’s full frame sensor (B).
And of course the medium format sensor just destroys all the other sensors out there. Got about 20 grand? That’s what it’ll cost to buy a medium format digital camera (as of this posting).
Four Thirds SLR is an intriguing option. It’s not too much smaller than the standard SLR sensors. The advantage of the Four Thirds system is that it allows for much, much smaller SLR bodies. (There’s no bulky mirror system necessary.)
1/1.8″ (I) is what most consumer cameras have. Notice how much smaller it is compared to the SLR sensors. That’s why you get superior image quality from an SLR image sensor.