Brant, you were right -- something was off. I did a bit more testing this morning. I believe the errors I was getting were the result of the aperture blades failing to function properly. I tried the lens again this morning on the EOS R3 and EOS 5D Mark III, and the lens won't stop down past about f/2.2. Pushing the DOF preview button on the 5D Mark III makes the aperture blades close a little, but not as much as they should for that narrow of an aperture. Same thing happens when I take a picture on either camera with f/16 set -- I can see the aperture blades closing, but not to the point where they are supposed to. Taking pictures while narrowing the aperture from 1.4 indicates that there's no change after f/2.2.Originally Posted by Kayaker72
I think the earlier errors I was seeing were the result of the blades beginning to fail, but they hadn't failed completely yet, or somehow the failure simply isn't causing the error now (in my limited tests).
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