The body of a DSLR is the heart of the system, in the sense that it is the primary interface and that one generally has a single body (sometimes two), but many lenses. This is not to say that the body (or the sensor) is more important than the lens (indeed, the opposite in the case), but simply less variable.
Canon and NikonEdit
Both brands segment their line by price/target audience, and replace models on an approximately 2 year cycle. The entry-level DSLRs are the biggest sellers by a large margin.
The current ranges are:
/ 600D/Rebel T3i
|D40 / D60 / D5000|
|Prosumer/Enthusiast||60D / 7D||D90 / D300|
|Semi-professional (Full-frame)||5D Mark II||D700|
|Professional : High-speed||1D Mark IV||D3|
Notice that Canon model numbers are of the form "40D", while Nikon model numbers are of the form "D40".
- This table should not be read to mean that the corresponding cameras are directly comparable or even the closest competitors, but rather that this is how the manufacturers segment their lines.
- At first Canon also used a D- prefix, in the D30 and D60, but switched to a -D suffix with the 1D, presumably to reduce confusion with Nikon models.