ok i keep hearing different opinions on this subject, i just bought my first dslr. a 50d with 18-200 kit lens. i love this thing coming from a s2is bridge p&s. but what is this conversion factor. is the 18-200 actually 28.8-320. I have a rebel film camera that had a 28-90 what happens there. I have heard that for example a 10-24 ef lens will be 16-38 but a ef-s will truly be 10-24. sorry for the confusion.
Well, if you were to compare the FL appearance from a film camera to your 50D, it would appear that at 18mm on the 50D, you would have a 28.8mm on the film body. So essentially, the 28-90mm at 28mm on your film body would look like the 18-200 at 18mm on the 50D.
The EF and EF-S lenses are only somewhat interchangeable, as you can't use an EF-S on a 1D or your film body for instance.
Yes, a crop-sensor camera gives the effect of having a longer lens compared to a full-frame camera.
So, an 18-200 lens on an APS-C body, ie x 1.6 crop factor, is effective 29-320 in terms of a full-frame sensor like that used in the 5D. An APS-H camera, like the 1-series, have a 1.3 crop factor.
This is why there are many birding photogs who shoot with crop cameras like the 50D - they get more mm/$ out of their big-gun glass.
The sensor on the 50D is smaller than the 35mm film frame (24x36mm) by a factor of 1.6, so the lens gives a narrower field of view. The business of "equivalent focal lengths" is just a way of telling you what angle of view to expect if you are accustomed to shooting film or a full-frame DSLR. The true lens focal length is always what is marked on the lens. An EF-s lens is what it's labeled. The only difference is that you can't use it on a full frame camera because it doesn't produce enough coverage to fill the frame.
An EF 24-85 will produce the same range of views as an EF-s 24-85 on the same camera. You can only use both of these on a 1.6 crop camera. If you're comparing, say, a 5D with a 28-200 EF to a 50D with an EFs, the EFs would have to be roughly an 18-125 to have the same function.
billyjoel wrote:
I have heard that for example a 10-24 ef lens will be 16-38 but a ef-s will truly be 10-24. sorry for the confusion.
Just to be clear, that's the part that's confused and plain wrong.
Yes a 10-24 on a 1.6 crop body will "see" like a 16-38 on a full frame body,
but so will an EF-s 10-24.
Multiply all your lens' focal lengths (both ef and ef-s lenses) by that 1.6x crop factor and you will get your effective focal length. The crop factor is not in the lens itself but is caused by the smaller size of the image sensor in your camera, BUT, the ef-s lenses are designed with smaller elements and so CANNOT be used in a fullframe camera.
There is NO EF 10-24, it only exists as an EF-S lens. In any case, your EF-S 10-24 must also be multiplied by that factor to get an effective focal length of 16-38mm on a 1.6x camera. Your 28-90 will become a 45-144.
Part of what may be confusing is that while 'EF-S' lenses are specifically designed for the smaller APS-C format cameras (like your 50D), the focal lengths are not stated in 35mm-equivalents. For your camera, you can find this by multiplying the focal length of any lens (EF or EF-S) by a factor of 1.6.
Though Canon doesn't really make this distinction in its marketing (as does Nikon), it can be helpful if you just consider these cameras to be a different (dominant in fact) format altogether. APS-C cameras accept "standard" 35mm lenses, but it's the equivalent of mounting a medium format lens on a 35mm body.
billyjoel wrote:
thanks everyone, so to get a true 10-24 i would have to have a full frame camera, bummer
NO, again, you cannot use an ef-s lens on a fullframe camera and the 10-24 is an EF-S lens. The widest Canon EF lens is a 16-35 and 16mm on a fullframe is already pretty ultrawide. The Sigma 12-24 goes as wide as 12mm, but nothing 10mm effective focal length.
wing tong wrote:
NO, again, you cannot use an ef-s lens on a fullframe camera and the 10-24 is an EF-S lens. The widest Canon EF lens is a 16-35 and 16mm on a fullframe is already pretty ultrawide. The Sigma 12-24 goes as wide as 12mm, but nothing 10mm effective focal length.
The widest rectangular Canon EF is the 14mm f/2.8.
wing tong wrote:
I stand corrected, but still no 10mm effective focal length in the Canon lineup and the EF-S 10-24 still will NOT work on a fullframe.
Actually, you can change the rear lens mount (either that or file some part of the lens mount) and shave the mirror if necessary, and the EF-S lenses will work on a 1D, 1Ds, or 5D series. It has been done before.
Parker_Dawson wrote:
Actually, you can change the rear lens mount (either that or file some part of the lens mount) and shave the mirror if necessary, and the EF-S lenses will work on a 1D, 1Ds, or 5D series. It has been done before.
After all that surgery - if it works and you haven't broken anything - you will still get hellish vignetting due to the smaller elements used in EF-S lenses and your warranty will be worth less than the paper it is written on. Note, I would not suggest shaving mirrors to someone who's asking about what a 1.6x is.
I think we are pushing this just a tad off topic and confusing the issue for the OP which is to understand what the difference is between EF-S and EF lenses in regards to a 1.6x camera and how to use that 1.6x crop factor?
but, for those who don't follow links, the short answer is that a crop factor
means that you have the same FIELD OF VIEW as a lens of 1.6x the one you're using on full frame media (basically, it is as though you're cropping the outside portions of the picture, hence why it is called a "crop").
What is important is that while the field of view changes (50mm lens gives you the same field of view as about an 80mm lens on a full frame camera), the depth of field (area of the image which is in focus - think blurred backgrounds) does not change relative to full frame. This is important for portraiture and any other situation where you are trying to control the depth of field.
craighagan wrote:
What is important is that while the field of view changes (50mm lens gives you the same field of view as about an 80mm lens on a full frame camera), the depth of field (area of the image which is in focus - think blurred backgrounds) does not change relative to full frame. This is important for portraiture and any other situation where you are trying to control the depth of field.
While in theory that should be the case, there was a thread here last year, which showed crop cameras at certain FL's and f-stops compared to full-frame at the same FL's/f-stops.
In a nutshell, the FF has a shallower DoF, if I recall correctly. For example, f/4 on a full-frame had the same appearance (DoF) as f/2.8 on a crop at the equivalent FL.
wing tong wrote:
I stand corrected, but still no 10mm effective focal length in the Canon lineup and the EF-S 10-24 still will NOT work on a fullframe.
10mm on a Full Frame would be hyper wide. 16mm is ultra wide and the sigma 12 is extreme. if you want more feild of veiw than that then get a fisheye.
efs is produced to get similar range in FF that unavailable in 1.6x
example:
ultra wide angle on FF 16-35 - EFS 10-22
ultra zoom on FF EF28-200 - 18-200
macro on FF EF100 - EFS 60
and so on
as above. Just multiply any focal length by 1.6 to get the effective field of view equivilent. However you still have a lens with the characteristics of the shorter length giving greater depth of Field.
Widest anyone goes in a full-frame rectilinear lens is 12mm, though there are some smaller circular fisheye lenses.