Apple caused quite a stir with the announcement of their Pro Display XDR, a High Dynamic Range display that occupies a convoluted space in the market. It seeks to be both a Very Nice Computer Display, and a reference HDR video monitor — but by most measures it’s far too expensive to be the former, and not quite up to the rarified specs of the latter. Confusingly, it also outperforms some HDR displays costing considerably more, by some metrics. It’s currently the only display-only device Apple makes, and it’s simultaneously ludicrously expensive and a too-good-to-be-true deal. Suffice it to say that while there may be very few people for whom the Pro Display XDR is the unquestionably right choice, they know who they are, and they don’t need the internet’s advice about it.
When I watched the announcement of this display, I was curious how Apple would handle an HDR video monitor that was also tasked with the mundane duty of displaying your email and a web browser. Was Apple planning on rendering the 255-255-2551 “white” of Google’s home page at one brightness level, and the HDR overbrights from a video clip at a much brighter level, right next to each other, on the same display?
HDR In Situ
The answer is a resounding “yes,” and the effect is both impressive and a bit unnerving. Below is a photo of a Pro Display XDR casually presenting the Finder thumbnail of an HLG clip I shot on my Sony a7RIV. The sky is radically brighter than the “white” pixels above it.
The screenshot of the thumbnail reveals where HDR values are clipped at “white.”
The photo, of course, cannot capture how startling this is in person. It’s like strolling through an art gallery and stumbling onto a painting with its own backlight.
It’s one thing to see HDR video on an HDR TV, where the entire image appears simply brighter and richer. It’s another thing to see this kind of imagery presented in the long-familiar context of a computer screen full of folder icons and file names. It’s probably the right way to handle HDR in an SDR world, but it’s strange and new, and possibly unique to Apple.
It also seems to be an important part of Apple’s ongoing display strategy. The company, long known for shipping high quality, color-accurate displays, is not reserving this HDR-in-an-SDR-world experience for folks shelling out $6,000 for a computer monitor. It’s also part of how all iPhone OLED displays are defined as HDR. Here you can see HDR video shot with an iPhone 12 Pro Max rendering the sky out my studio window as brighter that the “white” background of the Photos app:
Apple is commoditizing and normalizing HDR on their most popular platform, both in capture and display. And they’re not doing it just by making iPhone screens brighter. They’re making the right pixels the right brightness. It’s an impressive technical feat made all the more admirable by how natural it feels in practice.
Elderly Displays Rejoice
So Apple has a method of showing HDR and SDR content together on the same screen. It works on every display Apple bills as “HDR,” even though the phones are performing the stunt using a different underlying technology than the 32″ Mac display. The XDR uses “local dimming” to light up an array of LEDs brighter behind the HDR pixels, as needed. The OLED displays drive each pixel to the desired brightness individually.
Apple groups all this under one umbrella they call EDR, or Extended Dynamic Range. And even as they tout EDR as a selling point of their professional display and flagship iPhones, Apple has also quietly extended it to older Macs that were never advertised as being HDR-capable.
From Apple’s developer documentation:
Some Macs can process pixel data with a wider range of pixel values and send those extended values to the display. In macOS, the ability to process larger pixel values and display them is referred to as extended dynamic range (EDR). When you configure a Metal layer to support extended values, you can provide pixel values — and therefore brightness levels — that exceed the normal SDR range in order to display HDR content.
“Some Macs” is not limited to those connected to a Pro Display XDR. It includes my 2019 16″ MacBook Pro, and even my three-year-old iMac Pro. I think the limiting factors may be P3-gamut displays on Macs running Catalina or later. If you have such a Mac, you can try this at home.
Two HDR clips, one shot in Dolby BT.2020 with an iPhone 12 Pro Max, the other shot in HLG with a Sony a7RIV. In both the Finder and Quicktime Player on Catalina, the highlights in these clips should be visibly brighter than UI “white.”
If the Pro Display XDR is like finding a gallery painting with its own backlight, seeing HDR pixels popping off a Mac display you’ve known to be SDR for three years is like discovering a painting that’s been hanging in your house forever suddenly has backlight button.
Here’s another HDR clip happily blasting its whiter-than-white values on my non-HDR iMac Pro screen.
So add a third method of displaying EDR content to Apple’s roster: On these non-HDR displays, Apple has remapped “white” to something less than 255-255-255, leaving headroom for HDR values, should they be called for. The operating system is complicit in this trickery, so the Digital Color Meter eyedropper shows “white” as 255, as do screenshots.2
With Catalina, Apple quietly changed what “white” means for 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 battery life on it. When you map “white” down to gray, you have to drive the LED backlight brighter for the same perceived screen brightness, using more power. Apple has your laptop doing this all the time, on the off chance that some HDR pixels come along to occupy that headroom (or not: see update below). It’s a huge flex, and a strong sign of Apple’s commitment to an HDR future.
It also means that when you adjust your display brightness, macOS is commensurately adjusting the amount of headroom available for overbrights. Max out the brightness slowly and you can watch the HDR values gradually get pinched against the UI “white” as the headroom shrinks, until HDR white and Google white meet. Conversely, the lower your display brightness, the more headroom there is for EDR, although there will never be as much as on the Pro Display XDR, or even an iPhone 12 Pro.
This variance in EDR capabilities across Apple devices is where a defining feature of HDR display comes into play. HDR standards like Dolby Vision were designed to accommodate screens of varying maximum brightness. The content is display independent, and when macOS goes to render it, it first asks the display how bright it can go, and then builds a bespoke lookup for that output brightness, correctly displaying the content within the available range.
Apple handling this all for developers is a new kind of leg-up in the fraught field of color management. It’s actually trivial to display HDR content correctly on a semi-recent Mac. Apps such as DaVinci Resolve, Affinity Photo, and of course Final Cut Pro already do it, and you can expect to see it in Red Giant and Maxon tools as well.
Apple sells one very expensive, very capable device for displaying HDR — and literally millions of iPhones, iPads, and Macs that are also pretty darn good at it.
It’s an HDR World
I’ve been critical of HDR as a creative tool. My North Star is the look of film, with its glorious highlight rolloff. Trying to sell me “brighter” was like screaming at me in the front row of a Metallica concert that the sound could go louder.
In the words of the great Roger Deakins:
If you create a balance of light and dark on set you expect that balance to be maintained throughout the process. I personally resent being told my work looks ‘better’ with brighter whites and more saturation.
That was him talking about Sicario, five years ago. Since then, he’s shot a number of films, including Blade Runner 2049, which, damnit, takes artful creative advantage of HDR exhibition. For the most part, like Sicario, it intentionally occupies a narrow band of the available dynamic range. But at key parts of the story, certain colors eek outside of that self-imposed SDR container, to great effect. In a very emotional scene, brilliant pinks and purples explode off the screen — colors that not only had been absent from the film before that moment, but seemed 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 display, in many ways digital cinematography is still chasing the tremendous dynamic range and color fidelity of celluloid film. Properly projected film3 is, by any measure, HDR. So maybe I should warm up to digital’s latest efforts to live up to this legacy.
How much more orange could it be? The answer is none. None more orange.
Hug, Don’t Reject
HDR presentation joins the rich catalog of film techniques that can have a profound affect on audiences so long as they are not overused; alongside extreme close-ups, aggressive surround mixes, handheld camera work, fart jokes, and, well, just about every filmmaking tool from color to sound.
I suppose I knew this reality was coming. I guess I just wasn’t expecting to see it on my laptop screen, glaring at me between my email and my grocery list.
Update 2020-12-05
There’s good evidence that I’m wrong about EDR being speculatively on all the time on non-HDR Apple displays. Michael Fortin writes:
When the [EDR] preview first appears on screen, it is rendered normally, in SDR. It then progressively becomes brighter over the span of one or two seconds. Brighter than the surrounding white. This appears to be the EDR system firing up: slowly cranking up the display brightness at the same time as it darkens the standard white point for everything but the video. Those two operations are done in tandem so well that you don’t perceive any change on screen other than the video becoming brighter.”
I noted this transition animation on Twitter, but it's that “so well” part that tricked me — it is very hard to see UI white change at all during this EDR ramp-up, which feels impossible. More evidence: The screenshot borders I mention here are only EDR-white when there are other EDR pixels on the screen. The seamlessness of this transition completely fooled me, and serves as spectacular testament to how dialed-in Apple’s software and hardware are on matters of color.
Update 2021-06-11
For WWDC 2021, Apple has posted an excellent video on EDR.
I don’t love using this simplistic 8-bit nomenclature for RGB color values, but in this context I’m doing so to invoke an old-school familiarity (echoed by the Digital Color Meter app). Between high-bit-depth P3 displays, display color management, software calibration, and True Tone, it’s probably been a very long time since “white” in a Mac UI was truly 255-255-255.
If EDR reminds you of eLin, congrats on being old. And cool.
Something that, sadly, few people have ever seen.