Originally posted by channeler
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He reports problems with focusing. The Sigma 70-300 that I bought years ago was fine but is this another example of Sigma QC issues that people often report?
Sigma is, according to most users and a certain store here in Norway (which happens to be the main importer of Sigma), much better now than they used to be. There are stlll reports of problems with Sigma, but not much more than with other brands.
My 30/1.4 and 50-150/2.8 are both very good. The former broke down, but Sigmas service solutions are top-notch, really. I got it fixed from Wednesday to Tuesday the next week (broken focussing mechanism). It's really good not to worry about spending two months without a useful lens, and I don't think the rumors about Sigma is just nowadays.
Regarding Canon and Sigma, there has "always" been problems. Of course this does not happen to everyone, but front/back focussing was/is not uncommon with those two paired. Nikon and Pentax did not have the same problems (though QC issues in general). The reason may be that the on-board focusing motor and electronic aperture means more problems than relying on the body for doing the work. Not a bad word about Canon, but more complicated (for Sigma) often mean more problems, right?
Over to the topic lens, the "old" f/2.8-4.5 version did have some flare problems, hopefully the OS version is going to be better (and the "christmas light test" doesn't translate into flare resistance).