Angle of View for EOS digital compatible lenses

[alfred_maragh]

I am in the market for a zoom super wide lens for the 10D and

Digital Rebel. There are a number of such lenses available but I

want one with the widest field of within a certain price range

(below $600). I notice that there seem to be little direct

relationship between the lens focal length and its field of view.

For example the Sigma 17mm-35mm gives 103.7 degress at the wide end

while the Tokina 12mm-24mm gives 99 degrees. One would have expected

that the shorter the focal length the wider the field of view but

this appears not to be so. Does the 1.6 crop factor affect field of

view? If I want the widest coverage should I go for the lens with

the widest FOV rather than the shortest focal length? Thanks for

your responses.

[panos_voudouris]

Yes it does, the Sigma can be used with film cameras as well, therefore the FOV is 103deg.

The Tokina is for digital 1.6x crop cameras only, hence the FOV would be equivalent to a

12*1.6mm lens, which is 18mm, slightly less than the 17mm of the Sigma. As far as I

know, your only options are the Sigma 12-24 for the 10D (since it won't take EF-S lenses)

and the Canon 10-22 for the

DReb.

[steve_dunn2]

<p>Choose by focal length; assuming the same size sensor (which is a valid assumption for your 10D and Digital Rebel), focal length uniquely determines angle of view.</p>

[les]

Alfred, your expectation is correct. For a given format, the shorter the focal length - the wider the view angle. Usuallly the diagonal angle of view is quoted (a bit of cheating, but technically 100% true), sometimes the horizontal angle of view.

Here is the chart for Canon (and any other) lens. I seem to remember seeing and old version of this chart, where all three angles of view have been quoted: diagonal, horizontal and vertical.

 

http://www.usa.canon.com/html/eflenses/pdf/spec.pdf

[jim_doty]

Alfred:

 

So far as I know, the Tokina 12-24mm wide angle lens at $500 (USD) is the only super wide angle lens that costs less than $600 and will fit on both your 10D and your D-Rebel. It is new enough that it is still hard to come by in some places.

 

The Canon EF-S 10-22 lens is a great lens but costs more than $600 and it won't mount on your 10D.

 

The 1.6x crop factor does affect the field of view (and the depth of field and the hyperfocal distance). As has already been stated, all lenses have a smaller angle of view on digital cameras with a field of view crop than they do on 35mm film cameras.

 

I have an illustration of this in an article here:

 

http://jimdoty.com/Digital/fov_crop/fov_crop.html

 

There is a direct relationship between focal length and angle of view provided the lenses are on the same type of camera. A 10mm lens is wider than a 12mm lens which is wider than a 17mm lens and so on.

 

Happy Shooting!

 

Jim

[jimstrutz]

Just to make sure you don't miss the point, the Sigma 17-35mm gives 103.7 degrees when mounted on a full frame digital or film camera, not your 1.6x crop cameras. On a 10D or DRebel it will be about 75 degrees. The Tokina 12-24mm quote of 99 degrees is probably for 1.5x crop cameras (Nikon, Pentax, etc.). It'll be slightly less on the Canons (about 97 degrees).

 

A 17mm lens on a 10D or DRebel is only slightly wide. If you want superwide you will have to get down to at least 12mm. As has been pointed out, the Tokina 12-24mm is the only one available for under $600. Fortunately, it's a good lens for $500.

[alfred_maragh]

Thank you all for great responses. There is much clarity on the subject now. Steve, the link to the Canon lens chart was very useful. Jim's site has agreat article that comprehensively explained the topic. With all the info received from you all, I am now able to decide that the Tokina 12-24 will be my purchase.