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What do Apple’s latest updates mean for HDR photography? - Greg Benz Photography

  • ️@GregBenz
  • ️Thu Oct 17 2024

Apple recently release MacOS v15 (“Seqouia“) and iOS / iPadOS v18. There are several key changes which are significantly helpful for HDR photography, including:

  • support for a critical HDR file standard which should make it much easier to share images
  • greater support for HDR photos in native Apple apps (including iMessage)
  • better support for 3rd-party HDR monitors
  • improved tone mapping to support SDR or less capable HDR displays
  • support in Keynote (which you can use to create an HDR slideshow)

ISO 21496-1 gain maps:

At WWDC, Apple announced support for developer APIs to read and write gain maps using the upcoming ISO 21496-1 standard. Apple refers to this as “Adaptive HDR“, which is a great term for gain maps as they allow your photo to optimally adapt to any display. This is the key technology for HDR, as it allows us to support both HDR and SDR displays. Everyone gets the best possible image on their screen. And this concept may be used with all important file types (JPG, AVIF, HEIC, JXL, DNG, etc).

There are currently three different implementations of gain maps. The approach used by Google (Android) and Adobe is quite similar to each other, but not identical in practice. Apple’s own encoding is significantly more different, but conceptually similar. Ultimately, the files are not interchangeable and this creates confusing scenarios where HDR support is lost. For example, you can capture and upload gain maps on iPhone or Android to Instagram, so long as you use the same device for both. But you cannot currently upload the iPhone image from an Android and vice versa (thankfully, once you upload it works anywhere HDR is supported). So this mix of gain map formats has slowed adoption as it creates significant cost, complexity, and work for developers. And that’s why the ISO standard is so important.

The ISO 21496-1 standard recently reached the “draft international standard” phase, which should mean that it is close to official approval. It will take a little time before it makes an impact, but should help significant accelerate support for HDR on the web in 2025. Having a single standard will avoid failed uploads and should make it much easier for small developers to add support as standard software libraries add support.

This is a natural starting point, as it’s important to get viewing support before the images are worth creating and sharing (I am unaware of any software which currently supports creating images in the ISO format). So while Apple’s ISO support has no immediate impact today, it is a huge step forward that prepares Apple for the future of HDR but should help generate increased interest in the format.

HDR gain map support in native Apple apps:

Apple is implementing support for the ISO standard in several key areas:

  • iMessage app.
  • Photos app
  • Preview
  • Quick Look

This includes support for all four apps in MacOS, iOS, and iPadOS. These apps all support the older Apple format, which is still used when capturing HEIC / JPG photos with an iPhone / iPad.

The support in iMessage is particularly important, as you can now simply text your HDR photos to friends and family.

Support for the Adobe / Google gain map spec has not been added. That’s probably not too important, as ISO should quickly become the standard used by everyone. But it does mean that you won’t be able to share your existing HDR iPhone images with a friend using Android, at least not without re-saving the file through software like Lightroom.

Brightness slider for 3rd-party HDR monitors / TVs:

Prior to MacOS 15, you could not control the brightness (SDR white point) of a 3rd-party HDR monitor or TV. Only Apple’s monitors and laptops had this ability. For many people, this meant that their display was often too bright for productivity work like reading email and HDR headroom was limited. This ability to change brightness was the one area where Windows had a clear advantage with its SDR / HDR Content Brightness slider, but that is no longer the case.

MacOS 15 now shows a brightness slider under System Settings / Display for any monitor in HDR mode. It’s incredibly simple, you just slide it to adjust the brightness of the monitor to make it comfortable to view under your ambient lighting conditions. This very simple change has several important benefits:

  • You can adapt the display to be more comfortable to use and more appropriate for editing prints, without turning off HDR mode. The old default was 203 nits, which is about twice as bright or more than ideal in most rooms without strong window light.
  • You’ll have more HDR headroom if you are able to dim the display for your room, which will often be the case.
  • You more effectively use a wide range of HDR monitors and TVs.
    • Prior to this update, the only optimal way to view HDR under MacOS was with a 14-16″ laptop screen or Apple’s $5,000+ Pro Display XDR. Those are still best in class displays with many unique benefits, but it meant a loss of HDR headroom when using 27-32″ HDR displays at price points which are affordable to most photographers. That’s no longer a concern.
    • This is particularly helpful for working with OLED monitors, which excel in dark ambient light. You can now get incredible HDR results from a 42″ TV that costs only ~$800 or less.
    • See recommended HDR monitors list for more info.

With this change, MacOS now clearly offers the best overall HDR experience in terms of both quality and ease of use. Kudos to Apple for opening up their system for better 3rd-party support here, this adds tremendous potential value for a large number of Apple computer users.

Improved global tone mapper:

Gain maps are absolutely offer the best image quality for sharing HDR images. They adapt in an ideal way to any display and leave you as the creator in complete control of the result. By contrast, if you view a simple HDR image without a gain map on an SDR display, it will be automatically adapted using a process known as “tone mapping”. In nearly all cases, a properly encoded gain map will offer more consistently high quality than tone mapping can achieve with an HDR (as it includes input from the artist to create an optimal SDR, allows for local adaptation pixel by pixel, and does not vary from one browser to the next). That said, some images may be shared as a simple HDR due to sub-optimal workflows, automation, or a desire to reduce file size. So you will encounter simple HDR images without a gain map on the web and the quality of tone mapping is still important.

The quality of Apple tone mapping prior to the recent release was, quite frankly, very poor. Highlights often lacked detail and color often looked cartoonish.  Thankfully, the latest updates to MacOS, iOS, iPadOS, tvOS, watchOS, and visionOS (including Safari) all include a new global tone mapper which is extremely good. Highlight clipping is reduced and color has been significantly improved. I would still say that the quality of tone mapping in Google Chrome is clearly better, but only by a small margin at this point. Most people would likely say the new Apple tone mapping is clearly much better, but probably would not notice any difference from the results in Chrome without a side by side comparison.

Support in Keynote

If you are updated to Apple Keynote v14.2 and have updated MacOS to Sequoia, you will be able to use HDR photos in your presentations. This may be a very handy way to show HDR photos in a slideshow on your TV.

What’s still missing?

Apple has established an outstanding ecosystem for capturing, editing, and sharing high-quality HDR photos. They have clearly been leading the way for HDR photography along with Adobe and Google. However, HDR photography is still fairly new and there are of course some opportunities for improvement across the ecosystem.

The key gap for Apple is Safari / WebKit, which does not support HDR photos in any format. While you can (and should) use Chrome, Brave, Edge or Opera for a great HDR experience on MacOS – that simply is not an option for mobile devices. On iOS / iPadOS, all browsers (including Chrome, etc) rely on WebKit. As a result, you cannot view HDR photos in a browser on your iPhone or iPad. You can see HDR photos in apps like Instagram or Lightroom, but lack of support for browsing HDR photos at this point is rather shocking. No one has put more energy or cost into creating great HDR displays than Apple, so hopefully we’ll soon get the browser software to properly use the incredible HDR displays they’ve been shipping in phones since late 2020 (iPhone 12).

There are a handful of important but less critical opportunities which remain to be addressed:

  • No support in tvOS or Airplay2 for sharing HDR photos on an AppleTV.
    • This would be incredibly helpful for sharing our HDR photos on the large HDR TV’s most photographers already own.
    • There’s no technical limitation here (as far as I can see), as we can already stream DolbyVision movies at 60 frames per second over Airplay, we just don’t have the software to send a still image.
  • Increased headroom on iPhone.
    • The new M4 iPad Pro’s XDR display is 1600 nits and supports up to 4 stops of headroom. Similarly the MacBook Pro’s XDR display is 1600 nits and offers up to 4 stops (5 if you manually set the SDR limit down to 50 nits, though that is not recommended).
    • However, there is only support for 3 stops of headroom on iPhone, even though it also has a 1600 nits OLED.
    • Below ~80% brightness, the headroom is limited to 3 stops because the peak 1600 nits are not allowed. Ideally, we’d have access to the full brightness until the phone gets to much dimmer values (it probably should be limited near the bottom of the brightness range).
    • Aside from any software concerns, competing phone displays have gotten much brighter. The Samsung S24 offers 2,600 nits. This isn’t a huge gain (as 3200 nits would only be one stop brighter than the iPhone), but it is definitely offers a visible improvement in the impact of HDR photos.
  • No support for HDR gain map thumbnails in Finder (Quick Look / Preview does support). This is just nice to have, as many photographers will likely rely on software such as Lightroom to navigate their images.
  • No support for profiling HDR displays in order to improve color accuracy
    • This is not an Apple-specific issue. There is no ICC standard for HDR profiling, so it isn’t an option on Windows either. If you create a custom profile under MacOS or Windows, you will lose HDR support. Your only option currently is to use a display which is very accurate out of the box, supports calibration in the display (such as an ASUS ProArt or most TVs), or accept limited accuracy / extra steps (you can toggle to SDR mode for an accurate display for printing)
    • Apple displays are so good that it’s quite optional, but that’s not the case for many 3rd-party displays – and many photographers have very high standards for accuracy.