So add a third method of displaying EDR content to Apple's list: On these non-HDR displays, Apple has remapped "white" to less than 255-255-255, leaving room for HDR values if needed. The operating system is involved in this trick, so that the pipette of the digital colorimeter shows “white” as 255 as well as screenshots.
With Catalina, Apple has quietly changed what "white" means to millions of Macs, and none of us noticed.
Think of it this way: this EDR display philosophy is so important to Apple that they are willing to spend the battery life on it. If you map “white” onto gray, you have to operate the LED backlighting with the same perceived screen brightness brighter and with more power. Apple will let your laptop do this all the time in case some HDR pixels take up that headroom. This is tremendous flex and a strong sign of Apple's commitment to a future of HDR.
This also means that when you adjust the screen brightness, macOS adjusts the headroom available for Overbrights accordingly. Slowly maximize the brightness and you can see the HDR values gradually being pushed against the UI “white” as the headroom gets smaller until HDR white and Google white meet. Conversely, the lower the screen brightness, the greater the headroom for EDR, although there will never be as much as the Pro Display XDR or even an iPhone 12 Pro.
With this variation of the EDR functions on Apple devices, a defining function of the HDR display comes into play. HDR standards like Dolby Vision were developed for screens with different maximum brightness. The content is independent of the display. When macOS renders it, it first asks the display how bright it can be and then tailors a search for that output brightness, correctly displaying the content within the available range.
Apple, which does all of this for developers, is a new breed of advancement in color management. Getting HDR content to display correctly on a newer Mac is actually trivial. Apps like DaVinci Resolve, Affinity Photo, and of course Final Cut Pro already do this, and you can expect it to show up in the Red Giant and Maxon tools too.
Apple sells a very expensive, very powerful HDR display – and literally millions of iPhones, iPads, and Macs that are damn good at it too.
It's an HDR world
I have criticized HDR as a creative tool. My North Star is the look of a movie with its glorious highlight rolloff. Trying to sell myself “brighter” was like yelling at the front row of a Metallica concert that the sound could get louder.
In the words of the great Roger Deakins:
When you strike a balance between light and dark on set, expect that balance to be maintained throughout the process. Personally, I dislike being told that my work looks "better" with lighter whites and more saturation.
It was he who spoke about Sicario five years ago. He's made a number of films since then, including Blade Runner 2049, which fucking uses the HDR exhibit in an artfully creative way. For the most part, like Sicario, it intentionally occupies a narrow band of the available dynamic range. But at key points in the story, certain colors appear outside that self-imposed SDR container with great effect. In a very emotional scene, brilliant pinks and purples explode from the screen – colors that were not only missing in the film before that moment, but were altogether outside the spectrum of the story's palette. Such a moment would not be possible without HDR.
Or would it? While there are certainly colors that digital projection can uniquely represent, in many ways digital cinematography still tracks the enormous dynamic range and color fidelity of celluloid film. Properly projected movie
is HDR in every way. Perhaps I should adjust to the latest digital efforts to live up to this legacy.