Canon Camera Lenses
Which Canon DSLR lenses would work with my EOS300 (film) camera?

Can I buy any of the Canon/Canon compatible lenses available for either/both Full Frame as well as the CMOS Canon DSLR and use it on my Canon EOS300 Film Camera?

On your film camera you can use all EF lenses. You can not use any of the EFs lenses. The EFs lenses are designed for cameras with APS-C sized cameras like your Rebel XSi. The 18-55mm kit lens for your XSi will not work on your film camera.

All of the EF lenses will work on either camera. Your field of view will be different though. The XSi due to its smaller sensor will give you more reach on the telephoto end. For example a 100mm lens will perform on your XSi as a 160mm lens would on your film camera. You will lose out on the wide angle end though. This is why the kit lens for the XSi is an 18-55mm lens instead of the 28-80mm lens that was the kit lens with film cameras.

For third party lenses look for lenses that do not say digital only or anything similar.

Canon Camera Lenses

Do Canon SLR film camera lenses fit on a digital Rebel digital SLR?

I am trying to find a good 50mm lens for my Digital Rebel and see that the film Canon SLR lenses are much cheaper.

Any of the Canon EF and EF-S lenses will work with your Rebel DSLR.

What will NOT work are EF-S lenses on the 1D and 5D series Canon DSLR’s or Canon EOS 35 mm SLR’s

NONE of the Canon FD or older FL lenses are usable with the EOS cameras