Processing photos for HDR emissive displays (no, not that old HDR!)

[julianv]

Some of the newer laptops, tablets, smartphones, and desktop monitors are capable of high dynamic range (HDR) display. These devices are terrific for viewing video content mastered in a compatible HDR format (Dolby Vision, HLG, HDR10, etc.). But the standards and file formats have been slow to emerge for HDR display of static photos.

In what follows, "HDR" does not refer to the well-known methods for blending multiple shots, made at different exposures, into a narrower dynamic range for print or sRGB web output. Here, HDR refers to any media format, software, or device that is capable of displaying images with a large color gamut and luminosity range.

My interest in this topic began when I acquired a 2021 M1 MacBook Pro. I noticed that the Affinity Photo app has features for editing images to exploit the HDR capabilities of the miniLED screen in this laptop. I made some HDR versions of single raw files from a Nikon D850 and the results were stunning. The resulting files look more like real scenes than any computer displayed images I have seen. You need to see this to understand my enthusiasm. And there's a bonus: editing images for HDR display is simpler. High contrast scenes often require extensive work, and compromises, to squeeze highlights and shadows into the brightness range of a print or a (standard dynamic range) display device. But when I tried the new HDR editing mode, a couple of quick adjustments to the exposure and black level sliders were often sufficient. Of course, there are still possibilities for creative enhancements.

For a far more detailed coverage of this topic, I highly recommend this web page from Greg Benz. He provides sample images, and some tests to determine if your screen and browser can support HDR.

And therein lies the problem: currently the browser, software, and hardware support for HDR is very limited. The current version of Affinity Photo can only export HDR images in the OpenEXR and Radiance file formats. Neither is compatible with the normal color management standards used by browsers and other photo editing apps. Even if you have another app that can load these files, the rendering of colors and tonal range will probably be wrong.

Adobe just announced new versions of Photoshop and Adobe Camera Raw that can edit in an HDR mode for export in the JPEG XL (aka JXL) format. They are currently calling it a "Technology Preview" only available on macOS. I have not tried it.

Of the most popular web browsers, only Google Chrome has proper support for HDR images. Chrome can display HDR files in the JXL and AVIF formats. But, as I write this, the current version of Chrome requires a special configuration flag to be enabled for JXL support (explained in the Greg Benz web page). Furthermore, Google just announced that they plan to eliminate JXL support in a future version of Chrome. Eric Chan posted some JXL samples here - view them with Chrome while you can.

I don't know of any photo editing app that exports HDR files in the AVIF format (at least, not on macOS). According to Benz, this currently requires a multi-step process with command line tools.

Some people are experimenting with embedding HDR photos in video files, or using hidden videos, to trick web browsers into an HDR mode. But this is probably not a practical solution.

So, it appears that the current situation for HDR is a "chicken and egg" problem. People like me, who have experimented with the technology, are eager to exploit it and begin sharing HDR images. But we are frustrated by the absence of standards, software, and hardware. The corporate players are reluctant to invest in development effort until they see significant demand. There are certainly other considerations. How can we provide content (files, web sites) that renders properly, whether or not a user has an HDR capable system? Does this require duplicating resources? Perhaps HDR will eventually become the norm, but the transition could be a bumpy ride.

You can download a few of my HDR images (OpenEXR files) from this site. But to see the images as I saw them, you need to open them in the same software and hardware environment that I used for editing:

M1 MacBook Pro with miniLED screen, running macOS 12 Monterey or macOS 13 Ventura
System Preferences (Monterey) or System Settings (Ventura) > Displays > Presets = Apple XDR Display (P3-1600 nits)
System Preferences (Monterey) or System Settings (Ventura) > Displays > Brightness = set to 50%

Affinity Photo 1.10.5
Preferences > 32 bit RGB Color Profile = Display P3 (linear)
Preferences > Enable EDR by default in 32 bit RGB views = YES

The macOS Preview and Photos apps will display the files in HDR, but the colors will be desaturated (compressed to the sRGB space). I have not tested the files on iOS, Android, Linux, or Windows.

More info on HDR editing in Affinity Photo can be found here and here. Note: I have no connection with Serif or Affinity, other than as a user.

Have you done any work with HDR photos? Got any tips? Insider knowledge of what's coming? Please share.

[Tuco]

I'd like to have a workflow to get my RAW files to display with HDR on my iPad Pro.  After experimenting with the new Camera Raw on a MacBook with XDR display (as in Greg's YouTube video) HDR seems to bring a lot to the table.

I got my hopes sort of up with the new iOS 16 and new MacOS, which "support" HDR AVIF files (as on Greg's web page).  The support is rather poor however, it shows the images at least, but not with the extra brightness, it squishes the highlights down to standard brightness (your loss of saturation comment I think).  If you open Greg's HDR web page in google chrome on a Mac with an XDR display, then you see the images as it seems they should be.  Rather disappointing "support" for AVIF on Apple's part.

I imported a AVIF file or two from Greg's HDR web page into the Apple photos app on my Mac (which syncs to the phone), and it indeed imports and shows them, but shows them with highlights squished.  What is obnoxious is that when flipping through photos on my new iPhone 14 pro (iOS 16), one photo at a time forward, swipe, swipe, swipe.... When you swipe to one of those AVIF photos - as it's mid swiping, it displays with full brightness (but briefly)!  When it lands on that photo, squished again.  But if you do that backwards from the next photo it doesn't do the same thing (so only one direction).  So the main trick is to get to an AVIF photo, then swipe left slightly (move finger right), but don't go all the way to the previous, so you're basically cropping the right of the image mid-swipe, hold your finger there and you can view part of the image properly at proper brightness (so long as you hold your stupid finger there part of the image off screen).  So Apple can display it properly on an iPhone, but they choose not to, so frustrating.  The same trick does not work on iPad.

I need to find some 10 bit HEIC images and try the same, maybe AVIF is too immature (with Apple software.)

[julianv]

I imported a AVIF file or two from Greg's HDR web page into the Apple photos app on my Mac (which syncs to the phone), and it indeed imports and shows them, but shows them with highlights squished.  What is obnoxious is that when flipping through photos on my new iPhone 14 pro (iOS 16), one photo at a time forward, swipe, swipe, swipe.... When you swipe to one of those AVIF photos - as it's mid swiping, it displays with full brightness (but briefly)!  When it lands on that photo, squished again.  But if you do that backwards from the next photo it doesn't do the same thing (so only one direction).  So the main trick is to get to an AVIF photo, then swipe left slightly (move finger right), but don't go all the way to the previous, so you're basically cropping the right of the image mid-swipe, hold your finger there and you can view part of the image properly at proper brightness (so long as you hold your stupid finger there part of the image off screen).  So Apple can display it properly on an iPhone, but they choose not to, so frustrating.  The same trick does not work on iPad.

I have not done much experimenting with HDR photos on iOS, but I did manage to duplicate the experience you described above. I transferred one of Greg's AVIF files to the photo library on my iPhone 14 Pro Max. The AVIF file is between two non-HDR files. If the AVIF file is loaded normally (centered on screen) it is rendered in non-HDR mode. But if I start to swipe to the previous or next image, and pause mid-way, then it renders in HDR mode. This is very weird. Seems like the iOS Photos App is capable of HDR display, but it's not fully enabled. Or it's buggy.

BTW, I tried viewing Greg's page, using the iOS version of Chrome. No HDR.

[Tuco]

I tried viewing Greg's page, using the iOS version of Chrome. No HDR.

Apple makes the "other" browsers on iOS use the Apple rendering engine, so not a big surprise (sadly).