Quick take: Canon R5 C firmware 1.0.4.1 brought great video improvements, including a much faster photo/video mode switch, Clear Scan and an improved C-Log3. But in the custom shooting modes, it turned on pixel shift, a feature this camera shouldn't have, and there was no way to turn it off. Standard manual mode seemed fine. I wanted Canon to confirm the camera was safe to use for photos.
Update: Canon pulled this firmware and released a fix. See Canon R5 C firmware 1.0.5.1 fixes the pixel shift bug.
The Good: Video Improvements
I have two R5 Cs, and I updated one before a weekend of shooting. The biggest complaint about this camera has finally been addressed. Switching between photo and video modes is now dramatically faster, while the camera on the old firmware still takes ages. Props to Canon for that.
Clear Scan is super helpful for stopping flicker when you're filming a screen.
C-Log3 is supposedly improved. My editor says it is, and I trust them.
Everything Canon promised on the video side delivered.
The Problem: Pixel Shift in Custom Modes
On the photo side, something popped up. When I switched from standard manual mode to a custom manual mode, which I sometimes set up for moving between indoors and outdoors, the camera started doing something I didn't recognize and wouldn't stop. Files came out around 100MB, and a small icon appeared in the corner.
It was pixel shift. That's odd, because the R5 C has no IBIS, so it shouldn't have pixel shift at all. On the regular R5 there's a menu option to turn it on and off, but on the R5 C it only shows up in the custom modes, and there was no way to disable it. Switch back to standard manual mode and it disappears.
Thankfully I had my X-H2S with me, so I switched to it for the rest of the event. Afterward I tested the R5 C in standard manual mode and didn't have any issues.
What I Wanted From Canon
I just wanted someone from Canon to say, "Don't use the custom modes, but manual mode is fine," or "Don't shoot anything important in photo mode until we fix it." In my experience, Canon is the worst of the camera brands at communicating with customers, and I shoot with all of them.
That matters because people buy into a professional camera line for reliability. The R5 C has a cooling fan and a cinema menu, and I love its codecs and video features, but I bought it as a hybrid camera for photo and video. I never had a problem with it before this update. If it locked up and I missed shots on a job, that would be a serious problem.
What to Do
If you shoot photos on an R5 C and already installed 1.0.4.1, stay out of the custom modes for now. Standard manual mode appears to be fine. If you haven't updated yet, it's worth waiting for Canon to address it.
