HDR and the Cinema

April 15

Early this evening I had the chance to help inaugurate a new AMC Cinema here in Las Vegas (AMC 18), where SMPTE treated us to the latest Star Wars movie, but more importantly, a series of clips from other recent movies rendered in what’s being called HDR. Tomorrow morning a panel of Pixar and Walt Disney folk will be talking about what we saw tonight and how it is already changing what they’re doing.

Most of you know what the letters HDR stand for: high dynamic range. The range from deepest captured shadow (black) to the brightest captured highlight (white). But sitting through tonight’s presentation I realized that a lot of you—especially you still photographers—aren’t thinking about HDR fully or necessarily correctly. 

HDR capture has existed for stills for quite some time, and now most of us shooting video are running some form of Log format to extend our captured range, too. As with the still side of image making, with video you take a wide capture and then post process it to your output. In Hollywood they call that kind of post processing “grading.”

So have you really thought about what you captured and how it will be displayed? After all, if you’re outputting mostly for computer screens, the lowest common denominator is 6-bit depth and uncalibrated sRGB Color Space to view, and very few people have anything above 8-bit and calibrated sRGB (I now use a 10-bit display with a Color Space similar to AdobeRGB). Not a very big output spectrum to work with. Heck, even with paper we can really only print about six stops of information. Again, limited output.

Wait, so why are we capturing 14-bit and running it through PhotoRGB Color Space when we post process? (Hopefully while viewing on at least a 10-bit monitor that’s been calibrated ;~). 

What most still photographers mean by HDR is that they capture as much of the scene brightness variation as they can, and then they spend all their time processing that data so that it compresses into a display technology that’s far, far smaller. With earlier digitized Hollywood theaters, that’s been true, too. 

I believe that Tomorrowland was the first feature that was mastered to the wider visible dynamic range and larger Color Space that SMPTE, Dolby Labs, and everyone else is calling HDR. The theatre in which we enjoyed the presentation is brand-spanking new and has everything necessary to display HDR-mastered features at the highest resolution. On a beautiful screen, with great seats and 13 channels of Dolby Surround Sound.

I wish you could have seen what I saw. I’m going to do my best to relate it, but words won’t do it justice. Moreover, unless you see the “before” (the way features used to be graded and projected) and the “after” (the new HDR grading and Dolby Cinema presentation) together you might not catch that anything is different, though you might somehow note that the experience was more intense for the latter. 

Inside Out—a Pixar animated feature that’s thoroughly enjoyable and I highly recommend—was one of the before/after samples used in the presentation. If you’ve got a copy of it, go ahead and play the opening right up through the first memory ball being sent off. 

The film fades into white. The storytelling is from the future, so there’s a very bright High Key effect used in this portion of the film. The film fades into white

So here’s how we talk about white on displays (or screens): nits. That’s a photometric measure of the luminous intensity per unit area of light traveling in a direction. Towards your eye. 

The first screening of Inside Out’s beginning was projected the old way: 43 nits. The second screening was projected the new HDR way after having been regraded for it: 108 nits. Yeah, that’s a big difference. And it was instantly and absolutely obvious to all in these back-to-back screenings. 

But there were other things that were easily noticed in the clips, too. Blues didn’t have a lot of nuance and differentiation in the original, but it was clear that we had colors extending the blue gamut quite a bit in the remastering. But the thing that struck me and those around me was the purples: purples actually looked purple. 

Moreover, it was also clear to me and the seat mate I was discussing this with that shadow color tones were better. A purple in shadow in the original tended to just get messy and indeterminate; a purple in shadow in the remix was clearly purple, and the right tone.

Chuckles the Clown has red lips (curiously, on Pixar’s Wikia for Chuckles, they look orangish). Those lips clearly were the usual “digital red” in the original, which is to say a reasonable approximation, but missing the brute force impact of fire engine red. In the HDR remaster red was red. To the point of being so beautifully red I wanted that color for the next time I shoot someone in a red dress, or a red Ferrari. 

Red in 8-bit RGB terms is 255,0,0. I’d swear Chuckles lips are 255,0,0. If you’ve ever tried to capture and then output that color, you’ll know why I was impressed. 255,10,0 doesn’t cut it. Our eyes often can see even a little contamination. 

So I walked away thoroughly impressed. Not a lot of movies have been mastered this way yet. And not a lot of theaters can show the HDR mastered versions of these films yet. But it’s coming: better-looking feature films that put a really broad range of tonality from black to white in your face in ways you won’t be able to ignore. 

While it’s only a part of what I wrote about above, Dolby Vision has a page where you can see some simulated before and after images (scroll down to “See Entertainment Come Alive”). I’ll just say this: those Web site simulations look a bit fake, overdone, and a bit surreal compared to the real thing on the screen done right, as it was in all the screenings I saw in Vegas. Still, they’ll give you some sense of what I was trying to describe: better color, an opening of the full tonality in the scene, and a clarity that accrues from those two things.

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