visuals on planetarium dome getting washed out

Copy-pasting from an email thread - 

Just a follow-up on the issues with washed-out visuals we were facing.

When slowly fading in particular scenes, we can clearly see a point where parts of the scene get washed out, with the projector suddenly jumping in brightness. Looks like this projector, Optoma ZK-507-W, has some poorly executed "high-brightness" handling, which we don't seem to be able to disable. As long as we keep large areas below 50% brightness, small bright areas like stars, trails etc can be viewed with good contrast. 

I think it is some sort of local dimming similar to what is used in some TVs, https://www.academia.edu/88311604/Backlight_local_dimming_algorithm_for_high_contrast_LCD_TV but with very poor results.

Perhaps a warning line can be added at https://paulbourke.net/dome/faq/#projectors for this projector, indicating its poor performance.

To which Paul replied,

I  assume you have tried

1. Turning off the DynamicBlack settings in Display ->  Image setting -> Brightness mode menu.

2. Turning off the HDR/HLG in Display -> Image settings -> Dynamic range menu.

Yes for the 2nd, there was no such menu for the first point. Since my source is not HDR, I also tried "Auto" in addition to "Off".

Also, have tried all the different modes, including "Film" - even that has the noticeable brightness jump once a large enough area has a pixel value high enough (perhaps >50%). 

(Interestingly, some planetarium shows have more problems than others.

Eg. Unseen Earth, https://www.unseenearth.eu/ - has some drone shots etc which look terrible on our dome if I don't mask out most of it to <50%

Mars - the Ultimate Voyage - https://www.bellmuseum.umn.edu/mars-ultimate-voyage/ - has gamma settings, lighting etc such that most of the show looks pretty good on our dome.

In our own productions using OpenSpace, https://www.openspaceproject.com/ , there seems to be a difference between scenes rendered on Mac and scenes rendered on PC (Linux). Maybe gamma differences.

These micro-organisms are rendered fine, while I had to darken these scenes rendered on Mac for Jupiter, Saturn and Europa to not become completely washed out.

Interestingly, this scene, rendered on Linux, is fine.)