All lenses that have a "ef" or "ef-s" mount can work on a canon 50d. Be mindful, if you decide to go with a fill frame camera later on, the "ef-s" lenses will create heavy vignetting on those cameras?
EF and EF-S lenses will fit a canon 500D.
One of the most compatible lens for Canon brands is APS-C 22x14mm. Also, another compatible lens for Canon brands is 36x24mm.
The Canon EF-S lens is compatible with the AE-1, as well as most of the other Canon SLRs.
For a Canon SD1300IS there is no compatible fish eye lens. The lens on this camera is not removable and therefore you cannot add anything.
yes all Canon cameras are compatible via lenses to each other
Yes with an adapter
No, the lens mount is completely different.
The Canon 70-210 is an EOS lens, therefore is fully compatible with the Rebel 450. Just remember that the 450 has a 1.6 crop factor making the lens 112-336mm.
The Canon EF 24 70mm lens is compatible with all current Canon SLR camera models. The standard zoom lens is a powerful lens set that is great for long distance shots.
Canon 40d or 50d
Yes, via a lens adapter available from aftermarket producers. All Canon FD lens to Canon EOS lens mount adapters will contain an optical element to provide correct focus at infinity. This is because the Canon FD lens flange focus distance (distance from the focus plane to lens mount) is shorter then the Canon EOS lens.
Product reviews on the Canon EOS 50D have been generally positive. A lot of people who own it have no or few problems with it and find it to be a good camera to own.
Canon offers a large variety of special zoom lenses. Check out their website for specific lenses for your camera body type. Canon offers a variety of macro lenses for fitting to EOS compatible bodies. you can check further at http://www.clickmacrophoto.com/lenses/canon-100mm-f2-8-macro-lens/