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08-03-2012, 10:19 PM   #1
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Just a couple Sigma 17-70mm f2.8 questions

Just a couple Qs about my 17-70

firstly, whats the dot between 24 and 35 on the zoom, is it marking a sweet spot or something?

and secondly the zoom is feeling a bit rough between 17 and 24. has anyone else experienced this? Is it normal?

thanks

08-04-2012, 03:14 AM   #2
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Do you have the older 17-70 f2.8-4.5 or the newer 2.8-4? I have the newer version and:

a. I do not see any "dot" on the zoom barrel between 24 and 35. The only thing I see there is "28". The only dot I see is the register mark on the knurled zoom ring that indicates where the zoom is set. It moves as the ring is rotated so could be anywhere depending on how much you have zoomed.

b. My zoom is smooth through the entire range. Roughness might indicate some dust or something in the mechanism. Is the lens new?
08-04-2012, 08:39 AM   #3
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i have the 2.8-4.5

yeah mine has the dot to indicate how much you have zoomed as well as one on the rotating part, between 28 and 35.

and yes the lens was new, had it for 3 months and dust is a possibility, is there a way to clean it easily?
08-06-2012, 11:22 AM   #4
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I've had my 17-70 for about 5 years and it is my favorite lens. I have that dot between 24 & 35. I've always thought of it as the "Normal" focal length for our cameras. If I assign it a number I usually say it's 30. I rarely use the numbers on the zoom scale anyway. When I do use them it is for taking multiple shots with minimal distortions for stitching together into a panorama. Usually, I pick that dot as the chosen focal length for this purpose.

As far as the roughness is concerned, I would guess it has to do with dust / dirt in the mechanism. My lens feels a little rough when I compare it to my DA* 50-135, but it has always felt this way and presents no problems for me.

Enjoy the lens.

08-06-2012, 09:43 PM   #5
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Interesting that the Forum has just posted a comparison of the 17-70mm lenses with a photo which clearly shows the "dot" present on the older version and missing on the newer. Now that I have seen it, I tend to agree with the above poster that it probably represents "normal" (50 mm FF, 33mm +/- crop) for that lens.

As for cleaning the zoom mechanism, if a good blast of air doesn't do it, I'd probably consider sending it in for warranty service, since it is only 3 months old. I wouldn't try to put cleaning fluid or anything in it. You will definitely need a sales receipt since the lens has been disco since 2010.
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