When Canon first started producing lenses they used the FD mount. In 1987 they switched to the current EF lens mount. This change made the FD lenses plummet in price but not in value. Check out Caleb Pike from DSLRVideoShooter.com shooting incredible video with his 5DM2 and 7D with these $20 Lenses. How do you do it? It's easy, you simply need this adapter that happens to be 63% off for just $30.