Monday, April 27th 2009

Problems with Sigma 17-70mm

When I got my Canon EOS 30D three years ago I decided to get the Sigma 17-70mm lens instead of the standard Canon EF-S 18-55mm kit lens.

Sigma 17-70mm 1:2.8-4.5

On the whole the lens has worked very well, but recently I’ve discovered some odd behaviour from it.

Focus hunting

Firstly, I noticed the other evening that it hunted endlessly for focus without finding it, even though I was aiming at contrast edges which I normally think it would find. Admittedly light was perhaps a little dim, but certainly nowhere near dark.

I’m still not sure if this is a new issue or if the lens has behaved like this all the time. To some degree I know it has, but the hunting I saw now felt worse than anything I’ve seen previously.

Incorrect/jumpy focal length reporting

The second issue I’ve had is this: When using the lens together with my 420EX flash the flash zoom head will keep jumping between different (incorrect) zoom settings. I suspect this is because of the lens sending incorrect focal length data to the camera.

Now I’m not 100% sure this is the lenses fault since I haven’t tried to reproduce the behaviour with another flash. The weird thing is that the focal lengths written to the Exif data in the photos seem correct.

Anyone else who has seen these issues with this lens?

3 Responses to this post:

  1. Barron says:

    I had a problem with my 24-70mm reporting the wrong focal length as well, it was under warranty so I sent it in and they replace some electronics, probably the part that senses the length!

  2. Anonymous says:

    I have the same problem. I got my 17-70mm the other day, and am using it on a 450d. If it is dim, it will focus hunt endlessly, or find a target which turns out to be out of focus. Very disappointed…

  3. Anonymous says:

    This may not be entirely related, but my 17-70 (used with EOS400D) has intermittently started not focusing at all at the long end of the zoom when trying to focus on subjects near or at infinity. It's like the whole camera shuts down, and is only reactivated if you switch to manual zoom. The camera and lens are currently in for repair to establish where the fault lies – camera or lens.