Should I return the lens?

Frantic_Inc

Frantic_Inc

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Lee
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I bought a Sigma 17-50 2.8 last year which was used on a 40d, and have been fairly satisfied with it. However, since getting a 7d results have been hit and miss. Portrait shots have lacked sharpness, seeming a bit out of focus.
Today I used the micro-adjustment feature to calibrate the two together. I also did this with my 70-200 2.8 which only needed minor adjustment.
What I found was that at 17mm the adjustment was +17 (it was front focussing by approx 18") but from 35mm to 50mm was only +3. Quite a difference!

Does anyone think this is good reason to take it back to Wex for another?
 
Returning the lens or camera? I doubt you will get far returning the lens after a year.
 
I doubt you will get far trying to return it. But if you contacted sigma they might recalibrate it under warranty.
 
Probably best to send it directly to Sigma yourself. Contact them here and tell them what you've just told us.
 
As above really, I don't think WEX will take it back for a replacement as you bought it last year.

As the lens is under warranty, then contact Sigma and see what they say.

Hope you get it sorted
 
Hi,

All lenses are built within a certain tolerance value. I would contact Sigma and tell them what micro-adjustments you have to make and check with them if its within their tolerance. The problems is this - lets say the manufacturers tolerance for the lens is + or - 10. Lets say your camera has a manufacturers tolerance of + or - 9 .
Then if your camera is working at +8 and your lens at +9 this gives a value of +17 which unfortunately is all within manufacturers tolerance values. This is Sod's law. What you would have liked is for your camera to be at -8 and the lens at +9 which gives an overall tolerance of +1, highly acceptable !!
Does this help?
James
 
Exactly. It's a law of averages - the two out of tolerance values should more or less cancel out or in the case of Sods Law they add up two form a problem. The problem for us is that the two individual values may still be within manufacturers tolerances but the sum of these lies out side them - hence the need for micro adjustments.
Still worth checking with Sigma !
James
 
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