I'm using a Canon D60 -- that's right, *not* a 60D, but the D60 (6MP), which came out in 2002. I haven`t really kept up with technology changes since that time. I know more MP doesn't equate to better pictures in any strict linear way, but . . . .
I'm wondering what advantages / disadvantages for stock photography there might be in buying a new 18MP Rebel T2i or T3i (or even the 12MP T3.) It's hard to find comparisons on-line with such an "old" camera, but some users said the D60 had great color saturation and fidelity compared to newer (circa 2005) cameras. Maybe that info is now way out of date. They also mentioned the D60 was pretty bad for low-light noise (at least in some situations) compared to newer (2005) models.
I shoot in RAW, and use Canon fixed-length EF lenses: 50mm f1.8, 28mm f2.8, 100mm macro f2.8.
I know there are things I would like about the new Rebels: First -- 4% spot metering would be much more accurate than the D60`s center-weighted mode. Also, probably better battery usage, faster AF and file storage. Larger prints possible with 18MP, if I ever want to try and sell large prints.
But overall picture quality is the main thing. Seems to me that if noise reduction has improved a lot in 9 years, the 18MP T2i should give me noticeably better detail (and smoother tonal gradation?) than the 6MP D60, at least in most areas of a shot. But I suppose that depends on whether my lenses can resolve all that increased resolution in the first place.
I also wonder how the Rebel's kit lens 18-55 IS compares to my fixed length lenses. The IS sounds great, but it's not a really big deal to me. I've read that it's not great zoomed out full.
The 18-55 IS kit lens is not even close to your fixed lens (in sharpness, colors etc.). The new cameras have ( like Afagundes says) more control over noise (RAW and JPEG), better colors, sharper even at base iso. The new cameras that you suggested are good cameras but i suggest to switch the letter ''D" and go for 60D ;)...
100mm f/2.8 USM, Quad core Workstation PC with 8Gb of RAM and Nvidia ...
I started with the original Digital Rebel, with a 6MP sensor, and am now using a 7D with 18MP sensor. When I go back to my original files from 2005, I am in no way disatisfied with them.
To me, the main advances in cameras boil down to two things: resolution, and ease of operation. If you don't need the resolution for large prints or cropping, then your camera is capable of shots as great as today's best...since composition, lighting and timing are so much more important that the camera. I don't think you will be wowed by improved color accuracy - I'm skeptical about the 12bit versus 14bit RAW adding much except a tiny amount of extra detail in boosted shadows. You will be wowed by the resolution gain if you look at 100% on screen, but it is much less noticable in a print.
On the other hand, there are a lot of operational improvements. Fast shooting, More shots on a battery. Bigger LCD, with better color and viewing angles. Bigger viewfinder and coverage. Instant on. Large buffers for shooting more at once. By far, my main justification for upgrading is a 100% viewfinder and speed of operation, plus microstock has added the need for higher resolution to stay current. Video is a fun plus I love for family.
Your lenses will easily be up to the task, especially the 50mm and the 100mm macro. For some thoughts on how old sensors hold up, see this blog by Kirk Tuck.
I bought a Rebel 550D / T2i and spent some time getting familiar with it yesterday. So far, I feel Brad's comments will be confirmed - "When I go back to my original files from 2005, I am in no way disatisfied with them." But I should reserve judgement on improved quality until I do more of my typical shooting outside, rather than mostly flash inside.
I think it was a worthwhile investment. The big, bright LCD display on the back is a *great* imrovement over the D60. So is the speed of metering and AF. Canon's "DPP" RAW editor looks pretty fast, and I may be able to skip converting to TIFF alltogether eventually.