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Old 20-07-2006, 01:32 PM
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Jonathan is offline
Join Date: Jan 2005
Posts: 442
Houghy, how about a 35mm f/2.0? 1/3 the price of the 17-40L f/4 and 1/4 the exposure time.

Originally Posted by rogerg
Oh one thing I don't like about these lenses - they don't stop at infinity. I don't understand why, but I am guessing it's common in new lenses. Something to do with infra-red photograpy? My old Pentax ones do stop at infinity and so I never had focus issues doing astro photography with them.

Hi Roger. One reason for this is that ED (Canon call it UD I think) glass changes size slightly with temperature so the position of infinty on the focus ring can change depending on the temperature. Only 1 of my lenses stops at infintity and it's a non-ED glass lens, the rest go past infinity, the longer the focal length the further past it goes.
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