Sigma 17-50 f/2.8 IS focus issue

Started Jan 8, 2012 | Discussions thread
007peter Forum Pro • Posts: 11,167
That is the risk with Sigma or Tamron lens on Canon Body

It is frustrating to say the least. I enjoy buying Tamron and Sigma lens for their value, but they do tend to have unforeseen focusing issue down the road. As canon release newer DLSR, expect to have more problem as canon like to alter its AF algorithm ever so slightly to throw off 3rd party lens makers.

I have both good and bad experience - depends on camera + body combo:

  • [Canon 30d + Tamron 28-75 f/2.8] works okay, accurate just very slow AF motor

  • [Canon 30d + Canon XTi + Tamron 17-50 f/2.8 (NonVC)] poor Lens would indicate to the camera that focus has been achieve, but in reality it is completely out of focus. This happen roughly 20-30% of my photos, even in daylight. This lens really struggle to find AF at night . Sometimes its see-saw for a whole minutes without finding a single AF points. This happen equally on both my 30d and Rebel XTi. I cannot trust this lens to perform

  • [Canon XSi + Tamron 17-50 f/2.8 (NonVC)] better. Canon XSi's Digic 3 processor seem to focus with more authority than 30d + XTi with Digic 2 processor on this lens. AF reliability also seem to improved. 9 points AF still throw this camera off, but center-point AF is more reliable than before. Overall, just okay.

  • [Canon XSi + Sigma 18-50 f/2.8 Macro] amazingly fast + reliable combo as good as my [canon 17-55 on XSi ] in daylight or night. The nigh time focusing speed is particularly impressive for a non-usm lens. This combo has no focusing issue at all. I can trust this lens to perform as much as I trust any canon lens. Which is surprising because Sigma is known to have more AF issue with canon body

  • [Canon T1i + Tamron 17-50 f/2.8 (VC) ] surprisingly good in all areas: (1) Speed is fast for a non-usm lens (2) Quiet compare to the loud non-VC (3) AF Reliability is Outstanding in both daylight or night. 9 points AF is fast and reliable in daylight, but at night, 9 points becomes indecisive and AF struggle badly. Switching over to Center-Point AF solves the problem. Where as my Canon 17-55 have no such issue. Overall, I'm impressed and its a keeper.

Though my various canon camera body, I never have a single AF issue with any canon lens:

canon 18-55 IS (Japan), 18-55 IS (Taiwan), 17-85, 28-135 (copy 1), 70-200 f4, 70-400 f4 IS, 17-55 f/2.8, 28-135 (copy2), 35 f2, 50 f1.8 (copy1), 50f1.8 (copy2), 85 f1.8, 100 f2, 200 f2.8

Canon lens cost more but you get what you pay for.

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