why have EF and EFS lenses?

is this just a way for canon to make more money?

why cant all lenses just be EF?

Here is the history lesson:

In digital photography larger sensors are much more expensive than smaller ones. In order to offer 'affordable' digital cameras like the 300D (dRebel) and the 10D Canon created the sub-frame sensor size known as 1.6X or APS-C.

Users soon discovered a problem with using these smaller formats. There were no available ultra wide angle zooms (analogous to the EF 17-40 or EF 16-35) for the smaller format. There were also no wide angle zooms available to replace the function of stalwarts like the EF 24-70, 28-135, 28-105 etc.

Some early users pressed the FF UWA lenses like the 17-40 or 16-35 into use and regular wide angle lenses on their 10D's, but these lenses had limited zoom ranges and slow apertures for their cost.

So along came EF-S. These lenses were designed to fit specific gaps in the 1.6X shooters menu. The EF-S 10-22 is the 1.6X users 17-40. The EF-S 17-55/2.8 is the 1.6X users EF 24-70.

By making these lenses EF-S (not FF compatible) Canon made them affordable. An EF version of a 17-55/2.8 IS would necessarily have to cost a lot more than the EF 16-35/2.8....a $1650 lens!. An EF version of the EF-S 10-22 would be physically demanding to make and would thus probably be expensive as hell and massively compromised in performance.

360° wrote in post #9843407
is this just a way for canon to make more money?

why cant all lenses just be EF?

^^^ THAT^^^ plus - Canon is not the only manufacture with a EF-S/ cropped frame lenses. Most of the major camera manufactures have their own lenses for designed for the smaller sensors too. 3rd party lens manufactures such as Sigma, Tamron, etc., make lenses for these as well. So no, its not a way for Canon to make money.

i understand, do other manufactures do this as well.... i went to a sony thing the other day and the rep told me that all of their lenses fit on everyone of their cameras regardless of crop or ff

360° wrote in post #9843488
i understand, do other manufactures do this as well.... i went to a sony thing the other day and the rep told me that all of their lenses fit on everyone of their cameras regardless of crop or ff

They fit, but you would not want to do this. Nikon offers the same.

So you buy your $2300 FF 12MP Nikon D700 camera. Then you place you small format lens on it and it works......as a 5MP small format camera with worse IQ than many cameras that cost half as much.

Same with Sony.

So while Canon's EF-S lenses don't fit their FF bodies, there is no loss.

oh ok, thanks for the clarification

The APS-C format cameras such as Canon’s Digital Rebel series and their 20D through 50D series plus the new 7D 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 of these lenses 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 film 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 (moving 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 “S” standing for Short back focus.

The EF-S lens mount is purposely designed to be different from the standard EF lens mount 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 (the mirrors in the APS-C cameras are significantly smaller than those in 35mm cameras and “full-frame” DSLR’s). Also, the 35mm film frame would have a dark circle around the edges and the image would be inside the circle (known as vignetting).

seaside wrote in post #9843486
^^^ THAT^^^ plus - Canon is not the only manufacture with a EF-S/ cropped frame lenses. Most of the major camera manufactures have their own lenses for designed for the smaller sensors too. 3rd party lens manufactures such as Sigma, Tamron, etc., make lenses for these as well. So no, its not a way for Canon to make money.

NONE of the third-party "digital-only" lenses use the EF-S specifications (specifically the short back focus) or make them so they won't fit on any standard EF camera mount. All of them will fit any EF camera mount, but they do usually vignette if they are used on a camera with a format larger than APS-C.