Dimming SDR white for an external HDR display?

[gregbenz]

One of the native features of Windows for external HDR monitors is an "SDR brightness slider", which modifies the EOTF from PQ to allow the user to adapt the SDR brightness. This is very helpful for a number of reasons, especially when trying to dim the display down to a level suitable for productivity work in a darker room.

MacOS only supports control of the brightness for Apple displays, and 3rd-party monitors do not have brightness controls on the monitor when in an HDR mode.

Does BetterDisplay have any mechanism to help control SDR brightness while still using an external monitor in HDR mode?

[waydabber]

Brightness control in HDR is display dependent. Some HDR displays allow DDC brightness control (for example my GP27U mini-LED display) in HDR mode, others don't (reference displays certainly shouldn't). The app can't easily move the around the SDR peak brightness around on a third party HDR display like Windows can or the way macOS can do on Apple XDR displays (where the SDR can be anywhere between 100 and 500/600 nits and the EDR range will adapt to that baseline). What it can do is to extend the SDR range up until peak HDR via various techniques (this is platform dependent) or apply dimming. Some techniques will clip HDR when this is happening, others leave HDR content alone (this is also platform dependent). There is some info about this here (focusing more on the extra brightness side of things, not dimming).

https://github.com/waydabber/BetterDisplay/wiki/XDR-and-HDR-brightness-upscaling

[gregbenz]

Thank you for the info. If it is possible for you to modify the EOTF so that MacOS can do something functionally similar to what Windows offers for external HDR displays, that would be very valuable. To confirm, there is no way to do this without modifying MacOS itself?

Currently, only the Pro Display XDR has this level of control on MacOS for an external display. It would be really nice to be able to more easily use other HDR displays with MacOS (there are many much more affordable HDR displays on the market, plus OLED options for true blacks). It would also allow greater HDR headroom, as the SDR brightness if often higher than necessary (for example, I have an ASUS monitor which shows SDR white around 200 nits and it supports 3 stops of headroom, but would offer 4 if I could just dim SDR down to 100 nits).

[jleaders]

@waydabber
Yes likewise my Samsung Odyssey G9 on Windows benefits from more broad range when I set the Windows SDR brightness to a minimum - same peak HDR brightness and much lower SDR white peak meaning a broader HDR range.
My Apple Display on Mac also benefits from reduced brightness, on Macbook Pro M2 XDR display I put the OS display brightness at 50% but HDR content still looks fully bright; much broader range.

Likewise I'm hoping to reduce the SDR white peak on Mac, like I do with Windows, with the external Samsung display with this tool, but it appears there's no option for it.

Also btw @gregbenz your HDR blog is invaluable, thank you so much! I use it to test HDR behavior and calibration constantly! Not to mention your photos are top notch! Excited to see instagram slowly roll out HDR.

[waydabber]

You should upgrade to macOS Sequoia, as it has an SDR brightness slider with which you can adjust the SDR peak brightness between 4 and 500 nits for supported third party HDR displays adjusting the EDR range. BetterDisplay (latest version) already uses this capability when running under Sequoia and combines it with HDR upscaling.

[gregbenz]

@jleaders Thank you!

@waydabber That's fantastic to hear, I hadn't seen that capability mentioned anywhere.

[waydabber]

Yes, it's a silent update, Apple probably does not want to promote such third party displays but still understands that many use them in the industry.