1 ACCEPTED SOLUTION
R5 and the software/firmware is most likely the culprit with the focus-timing.
I have totally out of focus group shots on a "trip of a lifetime." I was very disappointed. I have NEVER had this problem before. I used RF 24-105mmL AND then later duplicated the problem with a RF 24-240mm lenses and they both exhibited the same inability to focus when using the Canon remote RC-6 and a flash. However, no focusing problems happened when I just shot using the usual method of pressing the shutter with the ol' trigger finger and waiting briefly at the half-press to insure focus. The camera was on a tripod. ISO (100) and aperture (6.3), 1/250th, and focus position and distance to the subject remained constant. I used at travel flash (Canon 270EX) for all shots.
The first two images below are with the RC-6 triggering the R5 with the RF 24-105mmL and a 270EX. at the above settings. I had taken multiple shots of people prior to this, enlarged them, checked them, and they were fine. No reason to check every single shot. Since the exposure was good, and the focus square was precisely where it was supposed to be, I didn't check this group shot. That was a mistake. I took 10 shots like this and they all came out like this. See the first two images below:
Below, however, is representative of ALL the other shots that I took myself i.e., without the RC-6 and the R5 on remote trigger setting, using my finger on the shutter button and pressing half down to achieve focus before pressing to take the shot. This was the result: Perfectly in focus. I took about 50 shots like this (some before and some after the above out of focus group shots, with the RC-6 and remote setting.) All were perfect.
The only difference then, is the use of the remote RC-6. NOTHING else changed.
So here is my suspicion: there is a bug in the software/firmware that triggers the flash before the lens has focused. This would also point, on a more global level, to a timing delay possibly with the shutter itself, i.e., a focus-shutter timing problem.
While I appreciate the kind gentlemen Tim's suggestions about taking everyhting off, changing the data cards, etc.,etc., with all due respect, that is a bit of grasping at straws. When all things remain the same, you isolate the one thing that is different: use of the RC-6 as a remote trigger. That was THE only difference and it isolates the problem. There may be other issues with other people's usage/equipment used that trigger the same fundamental focus-timing problem, but this was a controlled experiment which isolated and demonstrated one single variable.
BTW, I've been using the RC-6 with a 40D, 5D MKIII and EF lenses for many many years. Not a single auto-focusing problem.
And since other people are obviously complaining about this same defect, I'd say Canon has a problem. I'd also suggest that, before anybody sends it in to Canon for a "fix", Canon needs to identify the problem (and admit there is one), then put out a service notice to all their customers who have the affected cameras, and then detail what the problem is, and request customers to return the cameras to Canon (at Canon's expense) for a prompt repair/upgrade/"fixing." That's SOP for systemic bugs that are discovered in manufactured products, or with the OS running them, like with any other electronic device.
It's a real shame, but I simply can't trust the R5 now using a Remote Trigger. I will continue to do ore tests, such as using the self-timer mode and see what happens, and also with 3rd party remotes (such as electronic remotes, rather than the RC-6's IR trigger.). But at this point, that's doing Canon's job for them...
