The first image is a still pulled from the color module in Davinci Resolve, and the second is a crop of that image showing the issue.
Video info: 10bit 422 HEVC internal, Clog3, Rec2020 color space, 4k120, iso 800
The artifacts appear in other clips of the same scene, but do not appear in 8K RAW footage of the same scene. Is pixel binning in the 4k120 mode to blame? I've shot that mode a lot in the past, and never noticed an issue.
Even if it is a reflection, it shouldn’t appear that way. It doesn’t look like a clipped highlight at all. And it’s not an issue with resolve, as it shows in premiere as well.
I’m going to conduct some tests back home to see if I can replicate this issue.
We are experiencing the same issue with some of our footage.
**Update** I was able to confirm this is with firmware 1.3.1, but after upgrading to 1.4.0, the problem persists. Updating the firmware did not solve the issue. We confirmed the problem with three different camera bodies using three different types of lenses. The problem occurs when shooting at 2.8 at 1600 ISO. When we drop the ISO to 800, the problem goes away. The problem only occurs on edges where the focus is sharp. I'm going to contact Canon to see what the deal is.
**Update** I opened a case with Canon and sent in sample footage and a still. They were extremely responsive and wanted more info, but Flyinskiguy wrote me privately and gave me the answer, which I relayed to Canon. I'm posting it below for anyone else who stumbles upon this.
The Answer is: Turn off Canon Log Sharpening. It was set to 3 in our cameras. We turned it off (set to 0) and all the issues went away. I also discovered that the sharpening was adding aliasing to fine detail like hairs. What you gain by the little bit of sharpening is not worth it. I recommend everyone turn it off. I alerted Canon this was happening. Perhaps they will address in a future update. Sharpening in-camera should not destroy your footage.