Yeah, it's weird. In HDR Game mode setting everything becomes super dim. OLED light is at 100. Not sure if this is normal, or what. In HDR standard it looks great. Game mode just kills the picture. It's the dimmest setting of the bunch.
EDIT: HDR Standard looks great. HDR Game continues to look super dim. I'm pretty tired and frustrated, so will worry about this tomorrow. This is doubly frustrating because I'm "upgrading" from an E6, since I wanted the lower input lag, and can't for the life of me get it to look as good as I remember the E6 being.
Mate I have a feeling I know what's up. Did you update the TV to the latest firmware? Are you using PC Input?
First things first, do NOT update to the latest firmware if you care about HDR gaming in PC input. Update to the latest firmware if you care about correct colors in SDR for PC input.
I recommend updating to latest firmware as accurate SDR color and low input lag is important for me. When playing SDR content, switch input to PC mode. When playing HDR content, switch input to anything other than PC mode, and play in HDR game mode.
To make sure that you are not experiencing any black level issues, do the following:
1. HD Deep Color is on for HDMI input
2. Set black level on PS4 to limited
3. Set black level on TV to low in HDR mode
4. In HDR game mode, make color temperature W45, sharpness 0, color gamut auto
5. In Horizon Zero Dawn HDR implementation is overly dark on OLED, turn brightness to 70-75 for dark room, 80-90 in lit rooms.
6. In Uncharted 4, brightness setting left at default of 5 is good for dark rooms, increase to 6-7 in lit rooms.
God speed
The poster on this page is, unfortunately for him, in the minority. His issues sound extremely bizzare because I have not read about his issue anywhere on AVS forums or in this thread. Scary stuff though. Game mode and HDR is working perfectly for me along with basically everyone else :/
Are you in the US? And did you update to the latest firmware LG released via the TV (was never available on web)? If you did upgrade to 3.60.09, I've not seen a report where HDR game is NOT screwed up in PC input...