I’ve previously reported on the Canon EOS 1D[s] Mark III “brain fart”, whereby exposures are off by 2 to 3 stops for no apparent reason.
The Sigma 50/1.4 seems to provoke this effect: in only two days of shooting, I experienced this problem repeatedly, perhaps as many as ten times. Sometimes the problem persisted in a subsequent frame, also unusual. This clearly isn’t the fault of the Sigma lens by itself since I’ve observed the fault with Canon EF lenses, but the rate of occurrence is much higher than I’ve observed with Canon EF. Unscientific, but I feel compelled to report it.
The image below was taken with auto exposure. I had dialed in -1/3 stop exposure compensation to the Canon 1Ds Mark III. The camera chose 1/30 for one exposure, and 1/160 sec for the other exposure, yet there was next to no framing difference. The 2 and 1/3 stop exposure differences is enough to ruin many images.
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