EF and EF-S Lenses

[matthewchj]

Hi. Besides the mounting, could anyone explain to me the differences between EF and EF-S lenses? Thanks.

[Nicole]

A little ways down the page, the Canon EOS Beginners' FAQ (http://photonotes.org/articles/beginner-faq/lenses.html) explains what EF-S lenses are and how they're different. For sake of convenience:
EF-S cameras thus support lenses with a shorter back focus distance than EF lenses, because the mirror swings further back. This is where the “S” comes from - EF-S lenses have shorter back focus distances. (ie: the back part of the lens can get physically closer to the image sensor since the mirror is smaller) Having a shorter back focus distance allows Canon to produce cheaper wide-angle lenses that work with the smaller image format of a subframe digital SLR, since it’s optically very challenging to create a wide angle lens with a long back focus distance.

But, EF-S lenses can't be used on full frame cameras because they are made to work with the smaller sensor, and will cause vignetting on full-frame sensors.

[matthewchj]

ok thanks.

[inkista]

A simpler way of looking at it is that because crop-body cameras have digital sensors that are smaller than a frame of 35mm film, EF-S lenses don't have to create as big an image circle to cover the sensor. You can, so to speak, move the projector closer to the screen and get a smaller, sharper image more easily. :) So, EF-S lenses can also be smaller and lighter than their EF counterparts.

But if you try and mount an EF-S lens onto an EF-only body (which can be done with a Dremel tool and a lot of nerve), you'll get vignetting (i.e., the corners of the photo will come out dark) because the image circle isn't large enough. And you might slap your mirror into the back of the lens, because it's closer to the sensor/film plane than an EF lens would be.

This is why it's possible to mount EF lenses onto an EF-S capable body, but not the other way 'round.

[wycombiensian]

I'm tempted by the canon 10-22 EF-S lens (or the similar but cheaper Sigma 10-20) for my Rebel XT, but I worry about the long-term life of the EF-S lenses. If it turns out the smaller sensor size doesn't stick, and Canon only produce full-frame sensors in a few years time, then will I be stuck with lenses I can't use.

Have Canon given any hints on the long-term plan for the smaller sensor size?

[mdwsta4]

the smaller sensor isn't going anywhere on entry level cameras.
if you upgrade later, simply sell the EF-S lens. simple as that. get the use out of it now if that's the route you want to go down.

[matthewchj]

Get the Sigma 10-20mm lens instead. I'm thinking of getting one myself.
It's EF mount so it can fit all Canon cameras. It's also about $200 cheaper.

Here's a review:
http://www.fredmiranda.com/reviews/s...&cat=37&page=1