I disagree. If ALL 3rd party lenses had the problem, we could blame this on Canon. Canon was changing things and it was impossible for 3rd party lens manufacturers to keep up.
However, some 3rd party lenses continue to work just fine, so it seems that Sigma just didn't do a good job of making their lenses "Canon EOS compatible."
Mr. Bill
Again, there is not enough information to blame the problems in Sigma. Showing that a correlation exists between two items does not show cause and effect.
My understanding is that Sigma has not paid a licensing fee to Canon, while some other manufacturers have. I would expect Canon to build support for all LICENSED lenses into their new camera bodies. This is a possible explanation of why some third party lenses continue to work.
If a third party is making a lens that mimics the capabilities of an existing Canon lens, the third party lens can identify itself to the camera as the corresponding Canon lens. If Sigma is building lenses that have no matching Canon lens, it cannot masquerade as a legitimate lens. This is another possibility as to why we see problem reports with Sigma lenses.
I'm just saying that 'bad reverse engineering' is no the only reasonable explanation for the reported problems with Sigma lenses.
The reported problems can easily explained as Canon's unwillingness to support third party lenses without receiving a licensing fee.
There seems to be a general agreement that current Sigma lenses may have problems when used with future EOS bodies.
Personally I don't have any Sigma lenses. I don't have strong feelings about Sigma. I just think it's unfair to blame Sigma engineers for these problems without compelling evidence. The evidence presented in this forum can be explained in a number of ways, some of which shift the blame to Canon.
Unfortunately, I suspect anyone who knows the true story can't discuss it without violating a non-disclosure agreement.
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