Canon 1DX MkIII. Auto ISO is all over the map, and occasionally producing wildly inconsistent exposures from one shot to the next. Consider the two attached pics. These were taken a fraction of a second apart. The first was taken at ISO 640 and is properly exposed. The next shot in the series the camera jumped to 1600 ISO and completely blew it out.
I did a screeshot from Lightroom so you could see some of the data. These shots were taken back to back in less than one second, nothing changed with the lighting on the field. This was shot in manual exposure with Auto ISO. Why did it blow out the second pic? This isn't an isolated incident, I've got several like this from this game. Heck, one of them jumped to 10,000 ISO in broad daylight, completely washing the frame out.
Spot metering does not work well for shooting sports in the situations you describe. It will work a little better if you tie it to the active AF point AND you consistently keep that point on the same part of the player but under dynamic lighting conditions where there is a huge contrast across a small part of the frame it will give you widely varying exposure values because it is looking at a tiny part of the scene which often switches from dark to light within a fraction of a second. Spot metering is really useful for static scenes where you have time to compose and evaluate scene lighting but that is the polar opposite of live sports shooting conditions.
Try shooting next time in a different metering mode, you will find that either the partial or center weighted average modes will work fine with auto ISO and prevent the wild variance you get from the spot being on a slightly different part of the scene. I prefer partial although I found that the 1DX III works surprisingly well with evaluative metering under some pretty lousy lighting conditions (strong side or backlighting with extreme contrast as the day transitions from afternoon to dusk).
These two shots were taken with the 1DX III and EF 400 f2.8 at a summer soccer conditioning drill. They are RAW files converted in DPP with NO recipe or additional processing applied, just reduced in size during JPG conversion. In the first, the camera chose ISO 160 and the second frame went to ISO 100 for nearly a full stop difference.
I had been using the 1DX III earlier that day to shoot some technical photos of electronic gear and used spot metering for that and I initially forgot to change that for the practice I shot. But this shows what can go wrong with spot metering during sports. The camera is doing what it was set up to do by the user but that isn't the proper metering for this type of action shot. I caught that setup issue quickly and switched to partial for the rest of the shoot and the 1DX III exposure was consistent and correct. I always shoot sports in full manual, usually with the lens wide open, and the ISO at auto. It works extremely well under partial and probably would also with center weighted average.
Rodger
