macobee wrote in post #10514771
may sound as a stupid q, but cant seem to find any list that ensures me if i buy a 5D that all my lenses are compatible.
Canon 70-200 f2.8
canon 16-35 f 2.8
canon 100 mm ef 2.8
canon 17 mm fish eye
canon 50 mm 2.8
if these are all compatible then i think I may pick up a copy this week..........
The simple answer is yes, all of those listed lenses will work on a 5D, or any EOS camera 
Canon has two mounts, the EF and the EF-S mount.
The EF mount is common to all EOS camera bodies, digital or film. It replaced the FD mount when auto focus became popular.
There is a huge range of EF lenses, made by Canon and third party manufacturers like Sigma.
The EF-s mount is much newer, and is simply an addition to the EF mount.
In order to produce wider angle lenses for the crop sensor camera bodies Canon developed the EF-s mount that positions the rear element closer to the sensor.
A camera with an EF-s mount will take EF and EF-s lenses. But a camera with an EF mount, will not take EF-s lenses. (for example the 5D has an EF mount, but the 7D has an EF-s mount).
Sigma, and a few others, also make lenses with a reduced field of view for use on crop sensor cameras, however they use the EF mount, not the Canon only EF-s mount.
This means you can use them on full frame cameras like the 5D, but you get a black frame around the picture from the smaller rear element of the lens and its reduced image circle.