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Old Jul 17, 2005, 1:24 AM   #1
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Heyo,

I was playing around with the idea of getting an EF-s 17-85mm (to add more reach in my general lens) so I've been messing around with an old Minolta camera (with a 35-135mm lens), and I noticed that from 85mm to 135mm (a 50mm difference), there isn't really a huge difference when you compare the zooming from 50mm to 85mm (only a 35mm difference). I was trying to think of some reason for this but I don't think any of them are even close. But seeing this makes me feel there's not a huge difference from 55mm on the kit lens to 85mm (when considering the crop factor).

So does anyone know why the wider focal lengths differ so much more with each mm than the focal lengths at the tele ends?

Thanks.
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Old Jul 18, 2005, 10:13 AM   #2
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Well, I'd say the angle of view (sorry, that's my own translation of the french "angle de vue")is proportional to the inverse of the focal length!

You can look here

http://consumer.usa.canon.com/app/ht...al_length.html

or believe the graph below which was generated with the same data...

do I have it right :??


Theblue curve is the angle and the pink curve is the inverse of the angle (in degrees and 1/degrees respectively).
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Old Jul 18, 2005, 12:35 PM   #3
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BoYFrMSpC wrote:
Quote:
I was playing around with the idea of getting an EF-s 17-85mm (to add more reach in my general lens) so I've been messing around with an old Minolta camera (with a 35-135mm lens), and I noticed that from 85mm to 135mm (a 50mm difference), there isn't really a huge difference when you compare the zooming from 50mm to 85mm (only a 35mm difference). I was trying to think of some reason for this but I don't think any of them are even close. But seeing this makes me feel there's not a huge difference from 55mm on the kit lens to 85mm (when considering the crop factor).
Keep in mind that the change in FOV from 55 to 85 is going to be comparable to going from 88 to 136 on a full frame 35mm. If you want some hard numbers to supplement your look through the viewfinder, check here for field of view for your EF-S lenses:

http://www.sweeting.org/mark/lenses/canon-efs.php

In FOV, the 18-55 is comparable to 29-88 on a FF. The 17-85 is comparable to 27-136. The above page shows the difference fairly clearly. BTW, the published specs for lenses are usually based on diagonal view, as I recall.

The other advantages of the 17-85 over the kit 18-55: somewhat sharper at all focal lengths, USM quiet/fast/internal focus, and image stabilization which works quite well--handy on a lens that you are likely to carry around without a tripod.
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