Canon's press material for the EOS 5D states that it "defines (a) new D-SLR class," when we're not usually interested in marketing talk. The EOS 5D is unlike any previous digital SLR in that it combines a high-resolution (35mm) full-resolution sensor (12.8 MP) with a relatively compact body (slightly larger than the EOS 20D, though in your hand it feels noticeably thinner). chunkier'). The EOS 5D aims to slot in between the EOS 20D and the EOS-1D professional digital SLR, an important difference compared to the latter is that the EOS 5D has no environmental seals. While Canon doesn't specifically refer to the EOS 5D as a "professional" SLR, it would clearly be attractive to professionals who want a high-quality digital SLR in a body that's lighter than the EOS-1D. It's also no doubt appealing to existing EOS 20D owners (although lets hope they haven't bought too many EF-S lenses...).