You can get adapters for the older lens, but the automatic functions are lost (focus and aperture).
May be worth it for some of Canon’s big teles, probably not going to be happy with one as a daily shooter as half the function of the camera is lost.
Depends how old it is, and how much effort you want to go do.
Any EF, TS-E, MP-E, any Canon AF fit Tamron, Sigma, Tokina, and Zeiss ZE lens will fit straight on.
Any pre 1987 lens will not fit onto a Canon EOS camera. They need to be adapted or converted and will only give limited results. Using FD-EOS adapters is possible, but you have to choose between losing image quality and losing infinity focus, neither of which is ideal.
If you shoot APS-C the best choice for FD lenses is conversion. This is because the smaller mirror on crop sensors does not hit the back of a converted FD lens. To do the conversion you actually need to take the mount off an EF lens and put it onto an FD lens, which is quite some work, so you should only do this if you’re confident about the engineering behind all this.
Finally it is possible to make FD lenses infinity focus with Canon full frame SLRs, however it involves shaving a chunk off the mirror, not something that is recommended with a $5000 DSLR.
It depends.
If it is an EF lens, no matter how old it is, it will fit on any Canon EOS camera
If is it an old FD or FL lens, then no, you cannot use them on an EOS camera.
Is there a reason you did not give us specifics on the actual lens? That would really help a lot in answering your question effectively.
You can get adapters for the older lens, but the automatic functions are lost (focus and aperture).
May be worth it for some of Canon’s big teles, probably not going to be happy with one as a daily shooter as half the function of the camera is lost.
Depends how old it is, and how much effort you want to go do.
Any EF, TS-E, MP-E, any Canon AF fit Tamron, Sigma, Tokina, and Zeiss ZE lens will fit straight on.
Any pre 1987 lens will not fit onto a Canon EOS camera. They need to be adapted or converted and will only give limited results. Using FD-EOS adapters is possible, but you have to choose between losing image quality and losing infinity focus, neither of which is ideal.
If you shoot APS-C the best choice for FD lenses is conversion. This is because the smaller mirror on crop sensors does not hit the back of a converted FD lens. To do the conversion you actually need to take the mount off an EF lens and put it onto an FD lens, which is quite some work, so you should only do this if you’re confident about the engineering behind all this.
Finally it is possible to make FD lenses infinity focus with Canon full frame SLRs, however it involves shaving a chunk off the mirror, not something that is recommended with a $5000 DSLR.