Sigma 10-20mm vs. Canon EF-S 10-22mm

[RiceBurner7720]

Now i know that on the Sigma there DC verisons which means that there is no 1.6x lens factor if you put it on the XT. But with the EF-S 10-22mm on the XT is there a lens factor?? Thats the only thing throwing me off from buying the EF-S. Because i know the 10-22mm is wayy better in the reviews i read. So whats better. I need some help from some perople who own them. Thanks.

[Mike Bell]

Not sure where you got your info from but I understood that any lens designed for Canon AF mounts has its focal length stated in 35mm terms so the crop factor applies to the Sigma just the same.

Check out this recent thread comparing the Sigma 10-20 and Canon 10-22:
http://photography-on-the.net/forum/showthread.php?t=132854

[re1ex]

http://photography-on-the.net/forum/showthread.php?t=132854

fstopjojo, states the canon is slightly "wider" than the sigma, so that should rule out a difference in the lenses.

as for if ef-s uses the 1.6 crop, I don't know the answer.

[Jman13]

Ok...there is no 'focal length in 35mm terms.' Focal length is focal length. Period. The Sigma 10-20mm is 10-20mm. The Canon 10-22mm is 10-22mm. That's it, end of story.

Crop factor is a way for people who are used to thinking of field of view of their lenses by the focal length to have a way to visualize how a lens will look on their APS sensor camera, if they're used to 35mm film. That's it. It doesn't change the lens in any way. It's just that a 10mm lens on your Rebel will look like a 16mm lens looks on a 35mm film camera (or a full frame digital). The focal length doesn't change.

It's just a different format. If you are not used to shooting 35mm, then don't worry about crop factor at all. Just know that <24mm = wide angle, 25-35mm = normal, 35mm+ = telephoto. That's it. On medium format, 80mm is normal! but that same lens is a short telephoto on 35mm and a longer telephoto on APS sensor DSLRs....but it's still 80mm. Essentially, 35mm is not a 'magic format' it's just that it uses the same lenses as the smaller sensor cameras, so they felt the need to state a 'crop factor' so users of 35mm would know how the lenses would work on the smaller format cameras.

[Mike Bell]

Thanks Jman for picking me up on my rather loose terminology. Let me try again.

My intention was to try and correct Riceburner's misunderstanding that "on the Sigma ....... there is no 1.6x lens factor if you put it on the XT".

Here we go (hope this is more accurate!):

The focal length of a lens dictates the size of the image projected on to the film or digital sensor. The size of the sensor in the camera body dictates how much of that image will be actually used - saved to the memory. As the XT has a smaller sensor (22x15mm) than the 'standard format' (35x24mm) we talk about a crop factor of 35/22 or 1.6. The image is 'cropped' . (This has the same effect on field of view as using a longer focal length lens - hence the confusion).

The bottom line is that all lenses put on a 'crop body' should have their images cropped the same whether they are made by Sigma, Canon or whoever. What Riceburner wanted to know is "Will I get the same field of view from the Sigma set at 10mm than the Canon set at 10mm?" The answer is yes.