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What Exactly is 'HDRx,' RED's In-Camera High Dynamic Range Mode?

Ryan Koo

01.19.11 @ 10:52AM Tags : cameras, cinematography, hdr, hdrx, red

For those unfamiliar with RED camera-native files, a common first reaction to ungraded footage is “this looks really flat.” Indeed, that is exactly the point: by capturing as much visual information as possible, the camera gives the colorist the most flexibility in post to push the image toward a desired look. Now, with a new mode called HDRx, RED has found a way to conjoin two adjacent exposures in order to give rise to a real-time High Dynamic Range moving image. So in terms of dynamic range, what’s one of the hardest shots for a camera to expose? Quite possibly a dark interior with a bright sunny day outside. To prove the mettle of their HDRx mode, RED released the following clip:

Without a HDR mode like HDRx, you would have a choice: either you could see what’s in the barn, or you could see what’s outside. Not both. That’s the benefit of a mode like HDRx, which can allow the next generation of RED cameras (both EPIC and SCARLET) to capture up to 18 stops of dynamic range (a good deal more than film’s roughly 15 stops, and double that of a DSLR’s roughly 9 stops). But because HDRx is in fact two conjoined exposures, it has a number of side effects, some bad and some good. Here, RED’s Jim Jannard gushes about the motion-rendering characteristics of HDRx, describing the frame-combining mode dubbed “magic motion:”

Shooting 24fps and 180 degree shutter on film or digital is an illusion. It is not really the way we see motion. Ask someone to stand in front of you and swing their arm over their head from one side to the other. If this was shot traditionally at 24fps at 1/48th shutter all you would see is a constant motion blur until the arm stopped. But that isn’t what your eyes actually see. You see both motion blur AND sharper references to the arm and hand all along the path. “Magic Motion” is much closer to what the eyes see… the combination of motion blur (A-track) and a sharper reference (X-track)… with the bonus of extraordinary dynamic range not seen in any motion capture camera.

Jannard is no stranger to hyperbole, but while everyone’s busy comparing the dynamic range of the RED and ARRI ALEXA cameras, this change in motion rendering will also be something to keep an eye on. Those who’ve seen it in action swear by it, but despite the name it will likely be something that is not “magic” — whether or not one uses HDRx and its associated motion rendering options will likely be very shot-specific. If you’re curious about HDRx and Magic Motion, check out Jannard’s post at REDUSER…

Link: HDRx™ Overview – REDUSER

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