zafra52 wrote:Are there enough improvements to justify an upgrade from the 30D to the 50D?
Only you can decide. Because I had the option to dispose of my 30D, I upgraded from the 30 to the 40, and have been very happy with it. There are incremental improvements from the 40D to the 50D. To recap some of them, have a look at DPR's list of
30D/40D differences and
40D/50D differences.
I'm considering upgrading my 40D to 50D only because I want to take best advantage of my upcoming Antarctic travels. Otherwise I'd probably stay with the 40D (and I might still do so).
I would suggest that the improvements from the 30D to the 50D make an upgrade worth considering, but the 30D still takes nice photos and you need to decide for yourself.
More importantly, do you think the technology in the 50D will produce similar quality images of the D700?
I guess that depends how you measure "quality". I wouldn't try too hard to compare 50D images to the D700, nor to the 5D.
Apart from the basic issues of number of pixels, noise levels at various ISOs, etc, there's the fundamental difference of 1.6x-crop to "full frame": the difference in the resulting magnification of the image projected by the lens means the way the DOF produced by the lens is drawn in the final image is a bit different.
There are so many factors to consider when comparing cameras: handling, image quality, high ISO performance, etc. If you're just looking at image quality at "normal" ISOs (up to 1600) I'd suggest that the 5D (Mk.I) and D700 will produce similar images. They're both full-frame so issues of lens/DOF behaviour are equivalent. And the 5D is a lot cheaper (although not quite as cheap as the 50D yet). But there are things that the D700 does better than the 5D: it's not all about the image quality with the cameras on tripods pointing at static subjects...