Creative Lessons Learned in HDR Grading

Insde outIn a panel that opened the Future of Cinema conference, a panel of creators from Inside Out and Tomorrowland discussed their experiences in creating their first HDR grades and their desires for next steps. This covered similar ground to the panel we reported from IBC, but in less detail (

The team from the animated movie Inside/Out, for example, said that they created two different looks for the “mind world” and the “human world”. The mind world tells the story that is going on in the main character’s head while the human world is what is actually happening too her. In the mind world, the team used the full range of luminance and exaggerated the wide color gamut possible in animation. This means some colors that were beyond the P3 color gamut and needed to be seen using an RGB laser projector. In the human world, they elevated the black and reduced the color saturation. The mind world featured a peak luminance of 60 nits with highlights going to 108 nits while the human world was capped at 48 nits.

The Tomorrowland team did the same thing having scenes that occur in Tomorrowland use more of the luminance range and color gamut. They ended up creating 3 “looks” and using the tone mapping and luminance maps in a great deal of the grading process.

The Tomorrowland team admitting to toning down the dynamic range of the sun and other elements to create a more conventional film-telling technique. But the HDR works well when you can use the wide dynamic range to move from outside to inside to outside a tunnel.

Both teams were careful to not use the higher luminance or color capabilities gratuitously. They were careful to consider where and when to use it and how it enhanced the story.

One of the worries the Inside Out team had was transitioning their grade from the HDR monitor to the RGB projector. Would the luminance map well? Would the transition from black to the first code value work well? It turned out to work very well thanks to the use of the SMPTE 2084 EOTF throughout the production which specifies absolute luminance value.

The teams agreed that the standard production today remains the SDR grade, but they do want to think about a transition to a world where the HDR is the standard. But there are lots of pipeline and infrastructure issues to get straightened out including wider availability of HDR monitors – not only in the production facility but for all decision makers in the process.

HDR mastering also highlights any deficiencies in the content. It may reveal over or under exposed content, artifacts or problems with visual effects. This means HDR monitors are also needed in the VFX houses and on-set to identify problems early. The on-set aspects also imply that DP, cinematographers, lighting specialists and other need to start to think about how they change their craft to acquire in HDR.

But starting with an HDR master potentially makes the creation of the many derivatives easier as you start with higher fidelity content. But the teams questioned if an automated process could be used for this. While they agreed that some HDR-to-SDR conversion can be automated by studying the differences between the two grades, some things will be hard to do without human intervention.

As an example, they pointed to the window that is behind a main character. In HDR, the details seen through this window are visible while in the SDR version they are clipped and blown out. The first question is how to deal with this in the HDR grade? Conventional film making and audiences understand that a clipped out of window means they need to focus on the characters. If those details are visible, is that a distraction for the story that needs to be softened – even in the HDR grade?

The next questions is “can the conversion to the SDR grade be automated”? Normal scaling of the luminance is not likely to create the look you want, so some manual intervention may be needed. Thirdly, how do you carry this modification as metadata down to the TV or set top box? These all remain unanswered questions.

Both teams love what the new RGB laser projectors can do for the 3D movie – whether in HDR or SDR because of the higher luminance levels it can be screened in and the reduced cross talk. They noted that some directors like 3D and some just accept it, but everyone loves HDR.

When asked about high frame rates, it was noted that brighter images increase the flicker fusion threshold meaning that strobing artifacts become more visible. Therefore, increasing the frame rate may be a good idea as you go to HDR, especially for the higher luminance scenes or where objects may be moving quickly. Variable frame rate solutions may come as a result.

It also turns out that mastering the movie in HDR for the theatrical release is quite different from mastering for the home video release. For one thing, the peak luminance in theater is around 100 nits but in the home, it can be 1000 nits. In addition, there is a wide range of HDR TV capabilities, so understanding how the home HDR master plays on all these variations is a big challenge when maintaining director’s intent. Disney said in the panel that there are no plans for home distribution now, but they are actively looking at the problem.

A second group of content creators then tackled a similar theme with experts who worked on the Jungle Book, Star Wars, Inside Out and Tomorrowland on the panel. This group echoed many of the same points but did bring up one new point. The mainstream approach is still to master for P3 and Xenon light source as this is the installed base of customers. But when this master is played on an HDR RGB laser solution, it looks different. That’s because many directors are “pink and magenta phobic” and these colors are minimized in conventional grades. The HDR grade brings back these colors, plus there is the issue of metameric failure, where colors are perceived differently on the two systems.

The conclusion is that while SDR remains the mainstream approach in theatrical movie making today, it seems inevitable that this will transition to HDR being the grading master. The only question is the timing. CC