no HDR Brightness Balance

The original poster isn't having issues viewing HDR content, but like many others who uses external HDR displays with Mac, we want the ability to adjust the brightness of the desktop and applications while in HDR mode. As it is now desktop, safari, photos, everything in MacOS that isn't HDR video is too dim, but in Windows 10 and Windows 11 you have a slider to adjust how bright SDR content is up to 500 nits.

Again the poster is asking Apple to implement the ability to adjust the brightness of the desktop and applications while HDR mode is enabled. This has been possible for years on Windows 10.

Hi 1mike12,

You'll want to review the information linked below to verify your configuration is set up correctly.

Play HDR video on Mac

"Supported external HDR displays

Use an HDR10-compatible display that connects to the Thunderbolt  or HDMI port of your Mac.

• DisplayPort displays: Connect to the Thunderbolt port.
• HDMI displays: Connect to the HDMI port. If your Mac doesn't have an HDMI port, connect to the Thunderbolt port using an HDMI cable and USB-C adapter such as the Apple USB-C Digital AV Multiport Adapter or Belkin USB-C to HDMI Adapter.
• Apple Pro Display XDR: Connect to the Thunderbolt port, if your Mac is compatible with this display. 

If your Mac doesn't automatically enable HDR for the display, enable it in Displays preferences.

Check your Mac

• Install the latest Apple software updates for macOS Catalina or later. Some HDR features are available only with the latest macOS.
• Choose Apple menu  > System Settings (or System Preferences), then click Displays. In Display Settings for the external display, make sure that High Dynamic Range is turned on. This setting appears only on third-party displays that support HDR10, not on built-in displays. If you don't want to use HDR, turn this setting off.
• Choose Apple menu  > System Settings (or System Preferences), then click Battery or Energy Saver. Click the Options button, if present. If “Optimize video streaming while on battery” is turned on, your Mac saves energy by playing HDR video in standard dynamic range (SDR) while on battery power. To play in HDR, connect your Mac to power or deselect this checkbox.
• HDR content might play at resolutions no greater than 1080p on Intel-based Mac mini, Intel-based MacBook Pro, and Intel-based MacBook Air models, depending on the HDR content and the display on which it is viewed.

Check your display

• Some TVs support HDR only on a specific input, such as HDMI input 2 or HDMI input 3. Check your TV's documentation for details.
• Make sure that your display supports HDR10. If the display has its own HDR setting, turn it on or set it to prefer HDR when available.
• Make sure that your display is using the latest firmware from the manufacturer. Check your display's documentation for details.
• In general, HDR quality is better on HDR displays that offer better brightness and contrast ratio, which results in a wider dynamic range. 

Check your media

If you're playing premium content from a third-party content provider, check with the content provider to be sure that they support HDR on your Mac.

Check your cables and other devices

• If you're using HDMI, make sure that the HDMI cable and any adapter you might be using with it both support HDR10. Apple recommends HDMI cables that have been tested with Apple TV 4K and a wide range of TVs, such as the Belkin UltraHD HDMI Cable. Compatible adapters include the Apple USB-C Digital AV Multiport Adapter and Belkin USB-C to HDMI Adapter.
• If your video connection passes through an AV receiver, sound bar, or other device before connecting to your display, make sure that the device supports HDR10 and is using the latest firmware from the manufacturer. You can test by connecting your Mac directly to the display."

Have a great day.