This a community of Canon owners -- so your question may not necessarily be answered by someone from Canon.
Your AE-1 used Canon FD series lenses. These were made exclusively for 35mm film cameras and the lenses are entirely mechanical. The aperture is controlled by the mechanical lever which interfaces with the body and focus is manual.
Canon switched to the EOS system which is electronic. Most EOS cameras have auto-focus motors in the lens (there are a few exceptions) and the interface between camera and body is now electronic, not mechanical.
Canon no longer makes cameras that use the FD lenses (also Canon no longer makes film cameras.)
Though it is "technically" possible to get an adapter (3rd party) to allow you to use an FD lens with an EOS camera body, it's not advised. The newer lenses are significantly better than the old glass, the camera cannot control the aperture on an FD series lens, the camera bodies no longer include focusing aids in the viewfinder (e.g. the split-prism focus) since nearly all lenses are auto-focus (you can get 3rd party focus screens which offer some focus aids).
The general recommendation is that you probably don't want to use your old glass with a new camera.
I also still have my AE-1 and some FD lenses... but it mostly now sits on the shelf to provide some nostalgia of a different age of photography and as a conversation piece.
Tim Campbell
5D III, 5D IV, 60Da
