What is the difference between the EF and EF-S lenses?

Hi all,

I am going to buy a Rebel Xti camera and I wonder if my old Canon 35mm EF lenses (from my old Canon SLR) will work just fine on Xti. Can someone please enlighten me on the difference between EF and EF-S lenses?

Thanks,
Antonio

EF-S lenses have a smaller image circle - sufficient to cover the cropped 1.6 sensors but not the 1.3 or full-frame (equivalent to film) sized sensors.

The XTi will accept any EF or EF-S lens - it is not limited to EF-S.

The APS-C cameras have a smaller sensor than a 35mm film frame. If you limit the lens selection to those lenses designed to fill a 35mm frame (such as Canon’s EF series lenses), you will find that there are no ultra-wide-angle lenses for the APS-C camera. The shortest zoom lens focal length in the EF lens family is 16mm. There are two primes that are a bit shorter, and one of those is a "fisheye" lens. NONE are what the average photographer would call "affordable".

To design an ultra-super-wide-angle lens such as a 10mm (non-fisheye) lens for a 35mm camera is a VERY expensive proposition, which is why there are none.

By making some changes to the design criteria - reducing the "film" area to be covered by the lens, and allowing the lens to project deeper into the mirror box (move the rear element of the lens closer to the "film"), it becomes much more economically possible to design lenses for the task. Thus, the EF-S family of lenses was born. The mount is different so that you cannot mount the EF-S lenses on cameras that were not specifically designed for them. If you modified the mount of an EF-S lens to be able to put it on a 35mm film camera, there would be a high probability that the mirror would crash into the rear element of the lens at certain focal lengths. Also, the 35mm film frame would have a dark circle around the edges and the image inside the circle.

Now that you have some understanding of what the EF-S lenses are all about - note that there are NO long lenses with the EF-S design as they aren't needed - you need to understand that focal length is focal length is focal length. An EF 50mm prime lens designed for a 35mm camera, when used on an APS-C camera, will provide you with EXACTLY the same image size as an EF-S 18-55 lens set to 50mm. If you could cobble together a mount for a Hasselblad 50mm lens and use it on a 20D, you would again have the same size image as a result.

I think its about 1 inch!!!

It protrube into the camera making it unusable by any canon camera other then 20/30D and DRebel/XT/XTi (300/350/400)