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02-08-2008, 02:20 AM   #1
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Sigma zooms focusing past infinity??

I bought a new lens today, a sigma 70-300 apo dg. I know its a low end consumer model but since I will rarely use it I couldnt justify spending much more on a zoom. I also own a crappy sigma 28-80 that came with my camera, Which I use quite regularly to massage the arch's of my feet. Both lenses focus past infinity which is annoying. I dont care about the foot massager but Im not happy about the new lens suffering in the same way. Does anyone own a sigma zoom that does this? Id be more interested to know if anyone owns a 70-300 apo dg that doesnt so I can take mine back and not put it down to a design fault

Cheers, Druitt

02-08-2008, 02:27 AM   #2
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It is not uncommon for (longer) lenses to focus past infinity. Lenses can expand/contract because of the temperature, so the infinity point will change. For instance, my Pentax F* 300/4.5 also focuses past infinity.

May I ask why this is a problem for you (do you always use manual focus)?
02-08-2008, 02:50 AM   #3
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Most modern AF zooms are built with loose tolerance and quite common to focus pass beyond infinity a little. You will get used to it.
02-08-2008, 03:36 AM   #4
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Fair enough, Yes I almost always use manual focus. I just figured it was a fault as none of my old lenses or primes do it. Thanks for your responses

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