5D3 AI-Servo Focus Issue

Hey guys,

Canon 5D3 owner here, motorsport/drifting photographer using Sigma 70-200 f2.8. Using One-Shot on static objects, the thing is really really sharp. However, occasionally on moving objects, AI-Servo misses a lot. It misses so much infact that I have problems finding where the focus even is on the frame?

Here's 2 shots taken in high-speed burst mode. 1st is massively missed focus, 2nd is usable, but still missed.

Focus point on both is on left headlight using spot mode. I double checked my alignment of the focus spot using the "AF Point Display" setting in-camera, which was near perfect on left headlight

EXIF; 1/40th, f3.2, 200mm, ISO100 on both
These are unedited RAW exported straight from Lightroom

Now yes; I know that I'm shooting at 1/40th here on a moving subject, so I'm not expecting every single photo I take to be tack-sharp. But the 1st photo is definitely not motion blur, its just massively out of focus.

I've tried a factory reset on the camera, different SD cards, different batteries, different lenses, I've gone through every single setting & AF setting I can find on the camera. I've read the manual back to front more than once now, there is absolutely nothing left I can think of.

I now just have mostly 1 question in my mind;
Should I get Canon to look at my camera or am I simply expecting too much from this camera?

I say that last part because I'm aware that the 5D4 and 7Dii (for example) have improved AF systems. Perhaps I'm asking too much for a 4 year old camera?

I'm also thinking of going with a 7Dii as a 2nd body due to improved AF and crop-sensor for improved reach without spending £££'s on more lenses, but that's another story...

Any advice/thoughts welcome. I'm secretly hoping there is a hidden menu about AF/AI-Servo that I haven't found that will solve all my problems, but I doubt it

Using the AF in spot mode isn't the best for high speed Servo AF. At least use the full point.
It may not help you in this case, but it's normally better.
-yself, I use the 1DX together with the Canon EF 70-200 mm f/2.8L IS II USM. I've found it to work very well. Have you tried that lens too? The manufacturers tend to optimize their cameras with their own lenses, for obvious reasons.

The thing is, it *can* be amazing. It just seems my keep-rate of sharp photos has been declining in the past few weeks, and when the focus misses it misses by a LONG way. I can't think of anything I'm doing differently

This shot was taken in LA early October. I'd say its basically perfectly sharp.

Photos from the 1st post taken last weekend in Wales.

This problem is most likely 1) your lens, 2) your AF mode, and 3) your shutter speed.

Try a lens with USM focus, get out of spot mode as AF is slower, and raise your ISO to get a bit more shutter speed.

I can use a 5d3 with fast moving floor sports tracking one player with AF locked, but I use a USM lens, using single Af point or expansion, and shutter speeds much faster. I have used the sigma in the past, but it cannot lock and hold AF fast enough in many situations.