The EF 400 f2.8 is one of my favorite lenses and it ALMOST let me down yesterday at football. I typically shoot football with three bodies and lenses (1DX III bodies with 400 and 70-200 f2.8 glass and 1DX II body with 24-70 f2.8) and as I was setting drive and exposure I found the 1DX III body with the EF 400 wouldn't respond to setting drive, AF, metering, ISO etc nor could the menu or images be displayed. AF also wouldn't work although it focused fine in manual focus mode and the power focus ring and focus preset memory both worked perfectly. I removed the camera battery and tried again and got the same result. But without the lens attached, the body worked fine and putting the lens on another body resulted in the same non-responsive behavior.
I was about to switch that body to an EF 200-400 f4 "extender" which is also a nice lens but it doesn't focus quite as rapidly as the EF 400 which had worked perfectly at the last game. Since there was no error message, it was odd to have that behavior and the camera happily took photos without issue as long as I manually focused.
I decided to try cycling the ring of focus stop switches that are arranged around the far end of the barrel and after cycling each of them several times the lens fortunately returned to fully normal operation. When I got home, I mounted my 300 f2.8 on a body and held down one of the focus stop switches when I turned the power on and that combo behaved in exactly the same fashion as the EF 400 had while malfunctioning. So an AF stop switch staying closed when it shouldn't appears to have been the root cause.
The EF 400 performed flawlessly during the game and I have done a lot of testing today trying to get it to fail again without success. I will send it in for a cleaning and checkup in February which is a time of year when I don't use it BUT I hope by then to have gotten one of the four switches to fail again. I will probably ask Canon service to replace that array of four switches even though they may never malfunction again.
My criteria for camera gear is that it perform at a high level AND perform without glitches. My 1 series DSLR bodies and L series primes and zoom glass have always met that criteria and even after this episode I still have a trust filled relationship with the EF 400 🙂
So if you notice these symptoms (largely non-responsive camera with no error message) while using one of the "great white" lenses with AF stop buttons, try exercising the stop switches even if you normally don't use them. It may save you during an event. I always bring some spare gear but I prefer using my planned primary gear setup when possible and a little quick logical analysis made that possible yesterday.
Rodger
EOS 1DX M3, 1DX M2, 1DX, 5DS R, M6 Mark II, 1D M2, EOS 650 (film), many lenses, XF400 video
