Color Management Part 23: HDR tone mapping in practise by Chris Zwar

With HDR, what you see is not always what you get

November 9, 2024

When John Lennon said “Life is what happens while you’re busy making other plans”, he might have been talking about plans for a video on color management. Apologies that it’s taken so long to get this one out, it was only supposed to take a few weeks after the previous video, not a few months. But life happens, and while I’m lucky to have been busy with work since posting part 22, this series has had to take a back seat to commercial projects.

Tone mapping gets complicated. And even though the basic concept is easy to grasp – we’re modifying a high dynamic range image for standard dynamic range displays – the many permutations and combinations start adding up to make it frustratingly complex.

In part 22 I introduced the basic concept of tone mapping, and the video ended by showing how we can use 32 bit mode with sRGB projects. But sRGB was never intended for High Dynamic Range, and so the preferred way of compositing HDR video is using ACES. But even here, ACES isn’t just a button we can click. Currently, we have three different ACES options in After Effects, as well as the original Adobe Color Engine.

This video continues directly on from the previous one, Part 22. And we still haven’t finished: in the next video I’ll demonstrate inverse display transforms, which are particularly important for AE users dealing with corporate branding colors.

Although ACES solves many problems for visual FX artists, especially those working in large production pipelines, High Dynamic Range can still be a minefield for individuals or small studios working on motion design projects. This series has been aimed at After Effects users and the motion design industry, which is currently in a frustrating situation. While all digital cameras can record High Dynamic Range images, and we have demonstrated that HDR compositing simply looks better, the majority of video deliveries are only required to be Standard Dynamic Range Rec.709. This means that if we want to use ACES for better looking, industry standard compositing, then tone mapping the HDR composition for SDR output must happen at some point.

While this is generally one of the main strengths of ACES, the process can make SDR videos darker than intended – a potential hazard for commercial motion designers. Indeed, sometimes it feels like video content in general has gotten darker over the past few years, and I’ve often wondered if ACES pipelines were to blame.

This series has definitely become much larger than I ever expected, and there are parts of this video that I actually wrote several years ago. The notion that “what you see is what you get” is no longer true when working with HDR, was one of the key points in my original plan. When I first discovered that After Effects cannot display HDR video in the user interface I was slightly shocked. It wasn’t something I had thought about, but it felt like it was a significant deficiency on Adobe’s part.

Color Management Part 23: HDR tone mapping in practise 2 — The elephant in the room: Currently, After Effects cannot display a HDR image in the user interface, only a SDR preview

It has taken me a few years to fully grasp the complexities, and acknowledge how integral the User Interface is to a massive application like After Effects. Fundamental changes to user interfaces are not easy! And yet, only a few weeks ago, Adobe launched After Effects 2025, built on a brand new user interface code base called “Spectrum”. While there are bound to be some complaints from anyone who has to adjust to the change, and I’m sure a few early bugs will need squashing, what this hopefully means is that After Effects now has a brand new foundation on which to incorporate future HDR features.

Right now, in October 2024, this video is accurate: After Effects cannot display HDR images on a HDR monitor. After Effects 2025 has only been out for a couple of weeks. But I’m looking forward to the time when this video becomes outdated, and After Effects is updated to support native HDR in the composition viewer. I have no idea when this will happen, and I can only assume that when it does it will have involved an enormous amount of work. But HDR is the future, and so it’s only a matter of time.

This is part 23 in a long series on color management. If you’ve missed the other parts, you can catch up here:

Part 1: The honeymoon is over

Part 2: Newton’s Prisms

Part 3: It’s all in the brain

Part 4: Maxwell’s spinning discs

Part 5: Introducing CIE 1931

Part 6: Understanding the CIE 1931 chromaticity diagram

Part 7: Introducing gamma

Part 8: Introducing Colorspaces

Part 9: The theory of a color managed workflow

Part 10: Using After Effects built-in color management

Part 11: Introducing OpenColor IO