How does MacBook Air's Liquid Retina Display (M2, M3) manage to display HDR content?

[sotosoul]

After a quick search online, I found several articles that mention the importance of mini-LED or OLED/microLED displays when it comes to HDR content. This makes sense to me, especially if you want to display normal and HDR content at the same time on different parts of the screen (while browsing HDR videos in Photos, for example). All that has to happen is to light up those HDR-content-showing pixels / zones a bit more than their non-HDR counterparts. All good.

How does it work with the typical led-backlight screens such as MacBook Air's Liquid Retina Display, though?

On my MacBook Air M2, the part of the screen showing an HDR video preview (shot on a sunny day) somehow becomes brighter than its surrounding areas, without any noticeable change to the backlight's brightness.

My theory is that the computer simply keeps the LED brightness a bit higher than what it needs to be for regular content, and let the LCD do relatively heavy dimming to the pixels that are supposed to display non-HDR content but lighter dimming to the occasional HDR ones. However, this sounds like a waste of energy, especially if no HDR content is being shown on screen.

What am I missing?

 

[DisplaysShouldntBeTVs]

My theory is that the computer simply keeps the LED brightness a bit higher than what it needs to be for regular content, and let the LCD do relatively heavy dimming to the pixels that are supposed to display non-HDR content but lighter dimming to the occasional HDR ones. However, this sounds like a waste of energy, especially if no HDR content is being shown on screen.

This is true, but it only does this when there is HDR content on screen to be able to conserve energy.

Once HDR content is removed from the screen, the LCD color brightness and the backlight dimming slowly both fade (in opposite directions) back to normal levels — in a smooth enough way that tries to make non-HDR content maintain the same brightness during the entire transition.

Interestingly, on some Intel Macs, this "fake HDR" can actually be disabled by holding Option when clicking the Display settings item and then unchecking "Allow extended dynamic range".

It does not look like HDR can be easily disabled on Apple Silicon (aside from workarounds such as creating a BetterDisplay virtual display mirror), as this option is not visible on an M1 Air and an M2 Air that I tried.

 

[StoneJack]

After a quick search online, I found several articles that mention the importance of mini-LED or OLED/microLED displays when it comes to HDR content. This makes sense to me, especially if you want to display normal and HDR content at the same time on different parts of the screen (while browsing HDR videos in Photos, for example). All that has to happen is to light up those HDR-content-showing pixels / zones a bit more than their non-HDR counterparts. All good.

How does it work with the typical led-backlight screens such as MacBook Air's Liquid Retina Display, though?

On my MacBook Air M2, the part of the screen showing an HDR video preview (shot on a sunny day) somehow becomes brighter than its surrounding areas, without any noticeable change to the backlight's brightness.

My theory is that the computer simply keeps the LED brightness a bit higher than what it needs to be for regular content, and let the LCD do relatively heavy dimming to the pixels that are supposed to display non-HDR content but lighter dimming to the occasional HDR ones. However, this sounds like a waste of energy, especially if no HDR content is being shown on screen.

What am I missing?

It does it well

 

[sotosoul]

This is true, but it only does this when there is HDR content on screen to be able to conserve energy.

This seems very likely! How do you know about this? Is there any documentation out there? Is it something that you’ve observed? Cheers 😊

 

[casperes1996]

This seems very likely! How do you know about this? Is there any documentation out there? Is it something that you’ve observed? Cheers 😊

Iirc Apple has talked about this in one of their EDR WWDC talks

 

[bill-p]

What am I missing?

If no HDR content is displaying on the screen, screen backlight matches the contents of the screen just like a regular display would.

If HDR is displaying, Apple very "carefully" pushes the backlight brighter while simultaneously dims SDR regions using tone mapping to make the brightness bump imperceptible to the user.

As a result, the HDR content will almost immediately sees the benefits while SDR contents remain unchanged on the screen.

If you use a fast enough camera to record the screen, you may be able to see this shift in brightness. I think it's happening so fast that most people just don't even notice, plus everyone tends to be distracted when HDR content starts and it becomes super bright (thus leading them away from noticing any changes to SDR contents).

P.S.: just use a high speed camera if you have one available. Preferably not your phone since you can't manually enforce exposure to see the brightness change.