Film to digital

Question

Hello, will my ef 75-3000mm 1:4-5.6 III lens that i used on my eos rebel film camera work on the eos t3i digital camera? i am planning to buy and i looked at bundles for 2 lens and noted one was efs 18-55 and the second lens was simply ef. thank you for helping

Answer 1

cicopo wrote:
The above information is NOT CORRECT. The most important error to point out is that EF-S lenses and their 3rd party equavelents are ONLY designed to work correctly on crop body cameras. They have a smaller light path than EF lenses. The S does not indicate they have a built in Stabilizer.
+1
The "-S" suffix on EF-S stands for "Short back-focus".  
An EF lens projects an image circle into the camera body which is large enough to completely cover the size of a roughly 36x24mm sensor (or 35mm film negative frame).  
An APS-C crop-frame sensor camera (all Rebel Bodies, the 70D, 60D, 50D, etc. and the 7D) have a physically smaller sensor.  The sensor is the size of "Advanced Photo System - Class" size film negative frame.  
Since the sensor is smaller, it's not necessary to project such a large image circle into the camera body.  These crop-frame lenses are designed to project a smaller image circle and, in doing this, Canon places the rear-most element of the camera lens slightly behind the lens mounting flange -- which means the lens slightly protrudes into the camera body.  The distance from that rear-most lens element to the sensor plane is the "back focus" distance.  These short back-focus lenses project a circle large enough to completely cover the APS-C frame, but not large enough to fill a full-frame sensor (not with adequate qualiy anyway -- most lenses project a circle far larger) you wouldn't want to use an EF-S lens on a camera with a larger sensor.  But it can also create a physical problem (not just image quality problem).
Since a larger sensor requires a larger reflex mirror, the rear-most lens element on an EF-S lens would technically be back far enough that the mirror on a full-frame camera would hit it when it tries to swing clear to take the shot.  To protect against this, Canon designed a bit of shelf/ledge in the full-frame camera that prevents an EF-S from even being able to "seat" on a full-frame or APS-H camera.  So basically not only should you not attempt to use an EF-S lens on a full-frame body, Canon designed the mount to prevent you from doing that by mistake.
Canon's designation for lenses with image stabilization built-in is the letters "IS" in the name.
Tim Campbell
5D II, 5D III, 60Da