Wednesday 01st November 2006 09:32:18 PM
After doing some simple test shots, I discovered that my Sigma 17-70 lens has front/back focus problem. Look at the photos shown below. Both photos were shot using auto-focus with centre AF point aimed at the single line in the middle of the frame. As you can see, at 17mm the lens focused in front of the line. While at 70mm, it focused behind the line. There is no such problem at all with the Canon 18-55 and the Tamron 70-300.
I called Sigma distributor, APD in Damansara Perdana. They said this is very common among Canon DSLRs especially the entry level model with plastic body. Reason being Canon unable to manufacture the 'flange-to-sensor' length to exactly how much they are suppose to be, in this case 44.00mm. But since I have no problem with the other 2 lenses, the problem should be from the Sigma lens itself.
The Sigma distributor asked me to send my camera body along with the lens to them and they will send them to Singapore for rectification. The solution is to write a set of data in the lens to compensate the focusing error. This will take a whopping 2-3 weeks! How can I live without my camera for such a long time?
Not convinced, I emailed Sigma Singapore directly and they replied promptly, explaining the same story to me. But this time they promise to get my problem solved within a week. 2-3 weeks down to 1 week is a big difference. 1 week is still ok for me, so I decided to send in the equipments today. Hopefully they would keep their promise.
Fingers crossed!
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