The brightness keeps adjusting itself

[simonwoods]

I bought a RetroTink 4K to enjoy the scanlines and mask effects of MISTer and my consoles at 4K.
I've got a problem that's really affecting my enjoyment.
After I add the scanlines and mask effects, I need to use HDR10.
But, after doing so, and adjusting the brightness to my liking, the brightness isn't stable at all.
Example: I start the Super Mario Collection rom on the SNES core. I enter the game menu with the game boxes.
Within a second, the brightness will have adjusted. And, it does this many times throughout the game.
The strange thing is, I have a real Super Famicom and it doesn't do this at all. It's perfection.
I have no idea what's causing the issue.
Any help will be greatly appreciated.

[limi]

Assuming you have turned off all other image processing in your TV’s menus, this could be the “DVD menu” protection of your TV. If it sees static images for too long, it dims the image. I had this issue with my LG OLEDs, and had to purchase a service remote to disable it.

[PikWik]

on your TV while youre playing the MiSTer or on the HDMI input of the MiSTer, go to your TV brightness settings > Local Dimming > and turn it off or at the lowest setting.

also be sure your TV is in game mode and the usual gaming TV settings

but this could also be a setting with the Tink. look for settings related to dimming or auto brightness

[Retro-Nerd]

If this happens instantly it could be indeed related to some "auto brightness", "AI brightness" setting.

[simonwoods]

Thank You very much for your advice.
I asked on MyLifeInGaming and got the fix:

@mylifeingaming
7 hours ago (edited)
''[Try4ce] You probably have dynamic tone mapping set on your TV's HDR/brightness settings. Try turning that off, or setting HGIG instead. I used dynamic tone mapping for a brief time, because it generally looks cool in modern content (though technically inaccurate) but I also started to notice the brightness adjustment in retro games in a way that annoyed me, so I went back to HGIG.

If it's not that, do you have VRR on? Some screens can flicker in darker shades when VRR is engaged.''

Dynamic tone mapping was on. Switching it off solved the problem. I also have standard mode on instead of game mode as I prefer it, but I'm leaving that as is.