I'm curious if someone knows what's going on. It feels to me like Firefox is showing the image in HDR but with the wrong gamma curve applied.
macOS puts a slightly higher brightness than it required and artificially (in software) changes absolute white (0xFFFFFF) to greyish color (0xEEEEEE). So when a HDR content is required it will remove mask around that content. Safari ideally, probably that’s on Firefox why tone mapping doesn’t work well
The video looks the same in both Safari and Firefox, whereas the images are dim in Firefox on both my MBP display and external monitor.