EF EF-S ? confussion

[megatronixs]

hi im new here ive been reading for a while and so far i like the site








anyways my question is about EF and EF-S i really want a 50mm 1.4 lens but i have an xt.


would there be a crop factor from what ive been reading there would be but i see yes's and no's


so the real question would be are all EF lens for full frame and EF-S for the apc-s

[Oren]

You have a crop body (XT) and therefore you will have crop factor with whatever lens you use - read: you will have crop factor with EF lenses as well as with EF-S lenses.


As for you second question:


Any EF lens can be mounted on any Canon body - Full Frame as well as APS-C


On the other hand, EF-S lenses can be mounted only on the APS-C bodies.

[Joel]

Canon started making EF-S lenses because these smaller lenses require less glass, thus can be produced cheaper.


The Canon 50mm f/1.4 USM <span style="text-decoration: line-through;"]will become ais equivalent to 80mm on XT, because of the crop factor.

[megatronixs]

ok thanks thats what i thought was happening


also i sure hope canon makes some more EF-S lens so far theres only four they have

[musickna]

also i sure hope canon makes some more EF-S lens so far theres only four they have

More than four - look here.

[wickerprints]

While price is part of the reason for EF-S, it is not the only reason, nor is it even the most important reason for its existence.


EF-S exists because with a smaller sensor format, it becomes necessary to reduce the back focus distance in order to design wide angle lenses. This is also the reason why EF-S is incompatible with EF-mount bodies. The mirror would hit the rear of the lens.


Furthermore, with respect to the focal length, it does not change depending on what body it is mounted to. A 50mm lens is always a 50mm lens. What changes is the angle/field of view, which depends on focal length, sensor size, and back focus distance. If you put the EF 50/1.4 on an APS-C sensor body, then the resultant field of view is roughly equivalent to an 80mm lens placed on a 35mm "full frame" sensor. However, the 50mm lens remains a 50mm lens.


The imprecise language of "crop factors" and "focal length conversion" has created a great deal of confusion and misunderstanding among photographers; for instance, they may mistakenly believe that an EF-S 10-22mm lens is no wider than the EF 16-35L, end up buying the latter, and being disappointed because they didn't understand that the equivalence is between 10-22 + APS-C versus 16-35 + full frame.


The one thing to understand about focal length is this: whatever number is printed on the barrel is THE focal length (or FL range) of the lens when focused at infinity, irrespective of what camera the lens might be attached to. These focal lengths are directly comparable to each other regardless of whether it is EF-S, EF, or whatever mount it is designed for. So don't say that the EF 50/1.4 "becomes" an 80/1.4. It doesn't, and it can't unless you take it apart.

[Joel]

Thanks for stepping in here wickerprints.


I tried to explain the case as bluntly as possible, but you're right, this causes confusion. Of course the lens doesn't become a 80mm, but has a comparable field of view.


Jo&euml;l

[scalesusa]

EF-S exists because with a smaller sensor format, it becomes necessary to reduce the back focus distance in order to design wide angle lenses. This is also the reason why EF-S is incompatible with EF-mount bodies. The mirror would hit the rear of the lens.

I do not agree that the protrusion of the EF-S lenseswas necessary!!It was done becauseCanon chose to do it this way.


All other manufacturers have had no problem creating APS-c lenses that fit without hitting the mirror.The most prominent is Nikon.


There are also 3rd party manufacturers that make reduced image circle lenses which do not protrude into the camera and fit on Canon full frame cameras as well as crop cameras.


Canon's poor decision has plagued people with confusion and prevented the use of nice lenses like the 17-55mm IS on other canon models like the 1.3 crop. Sure, they would viginette, but I'd still prefer that they fit.


Many people modify the EF-S lenses to remove the little protruding ring that Canon added just so they can mount the lens to other cameras like the 10D.

[megatronixs]

ahhh i get it now thanks wickerprints and joel





and as for me saying they only have four lens was on the canon site i only counted four thats why hah

[neuroanatomist]

All other manufacturers have had no problem creating APS-c lenses that fit without hitting the mirror.The most prominent is Nikon.

Right. Nikon is just the king of lens compatibility. Which kind of metering will work with that lens? Is the autofocus in the body or the lens? An autofocus G lens - does that work on a D5000? Thank goodness there are about 50 different compatibility charts on the Internet, including Nikon's own charts for each camera model - most of which have 6-10 footnotes - because they make the situation so much easier to understand. Yes, the Nikkorautofocus G lens doeswork on a D5000, but it only manually focuses. Yikes.

There are also 3rd party manufacturers that make reduced image circle lenses which do not protrude into the camera and fit on Canon full frame cameras as well as crop cameras.


Canon's poor decision has plagued people with confusion and prevented the use of nice lenses like the 17-55mm IS on other canon models like the 1.3 crop. Sure, they would viginette, but I'd still prefer that they fit.

You can add a thin non-Canon extension tube and use an EF-S lens on an FF body. Or use a 3rd party reduced image circle lens. Canon has decided not to allow branded combinations that produce images like this. That's their choice. There are workarounds, if you choose to go that route.