Got my R5 two days ago. Here are two interesting findings about the overheating:
1. I woke up this morning and wanted to import into my computer my photos from yesterday. It took about 10-15 minutes with the camera turned on and plugged into the computer to complete the process. Once this was done, I picked up the camera. Naturally, it was not hot. But when I checked into the video mode, My remaining time for shooting in 4KHQ 24p had gone from 25 minutes to 10 minutes.
At first, I did accept the limitations on paper. But seeing this, I feel like I almost got scammed from Canon. They didn't have the right to advertise 4KHQ with that kind of performance.
2. In the afternoon, it was 34 degrees out. I left the R5 in the car for 3 hours, in the sun. When I came back, it was boiling, and I could have almost cooked an egg on top of it. I turned it on thinking I would have 0 minute left of shooting. Well, I have the full 25 mins left, and same for 8k. Go figure !
My thought is that it's probably the best hybrid camera available right now. But if canon doesn't fix this overheating issue fast, I will most likely switch to the A74 when that comes out, if the rumors turned out to be exact. By that I mean at least 20MP for stills, and 4K 10 bit 24p for video.
I really wanted to love that camera, and although its great for still, the video performance is making me really sad.
I don't remember the last time I plugged a camera with a wire into a computer to transfer files outside of work, which is probably also why I don't understand why people are so gung-ho about USB-C charging. I'd rather not risk ruining the port or some other assembly on the camera that'll cost hundreds to replace in the case the wire gets snagged, etc.
The R5's closer competitor isn't the A74, it's the A7R4, which has more limited video features than the R5. And if the past is any indication, I'd also agree that the Sony would be better for video... but the A74 is slotted against the R6, which doesn't overheat when using 4K24 (similar to quality of R5 HQ) with an external recorder accord to Gerald Undone's latest tests. So you have the same dichotomy in Canon that you have with Sony. The higher IQ cameras are prone to overheating due to their higher resolution sensors that require more processing. The A7S3 is optimized for 4K with a 12MP sensor, and the A74 will fall somewhere in between. The bigger limitation I see with the R5/R6 is that only Clog is available and not Clog3, which preserves more DR. That and the record limit of 29:59 are limitations in the R ecosystem that are not in Sony's ecosystem.
Personally, I've been burned by Sony. First with an expensive DLP TV that had issues that Sony finally acknowledged but they killed off the line so they never had to fix it, and now more recently with one of their "Tough" UHS-II card. I had predominantly used SanDisk without issue, but I was tempted by Sony's higher speeds and how many have recommended the Tough cards. But then I had 3 file failures in 2 weeks with low-level formats in between. Of course, mine wasn't in the batch that was "recalled" but it also failed shortly after the warranty expired. I've had issues with my Canon gear, but Canon has always been able to fix (some under warranty and some not) them at reasonable prices. If I had only 1 camera body a couple consumer-grade lenses, then I might "risk" Sony, but I'd consider it disposable. But not with multiple bodies with lots of lenses. I'm just glad that Canon closed the "body gap" for stills. Canon may not have "won" video, but as of now, it's video is competitive as opposed to DOA like the 5D4/original R. What other FF MILC has 8K? Will I use it? Probably not, but now I might actually start using 4K instead of 1080P, and that is an upgrade. Do I need 4K HQ? Probably not... usually my videos are of the kids performances where I leave the camera on a tripod (with the start/stop in breaks to deal with the video limit). Is 4K HQ sharper and less noisy? Yes... but I'm not cropping video and at TV viewing distances, it should be OK. Perhaps I'll pick up an external recorder down the line, and by then maybe there will be an aftermarket solution (i.e. tilta cooling fan). Or perhaps Canon will release a RF camcorder. These ARE interesting times.