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What is dynamic range remapping?


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Cinematographer Isiah Donte Lee shot this commercial and I loved how down the levels are. I reached out to a friend to ask how to achieve this sort of look, and in addition to knocking down a lot of level outside and choosing the right time of day, he mentioned that the DP rated the camera at 2500 ISO and did what is called "dynamic range remapping". I've looked online but haven't found any resources explaining what this is, so I was curious to see if anyone here has some answers and resources to point me towards for more information to deep dive into?

 

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I don’t have any specific info but if I had to guess what ‘dynamic range remapping’ means, I would assume that it’s just applying a custom gamma curve to the log footage before doing the Rec.709 transform to accommodate the extreme underexposure. Probably a big lift of the mids and shadows combined with chroma denoising?

It’s not totally clear whether the DP just rated the camera at 2500 EI and while recording at the native ISO and did the push in post, or actually set the camera to 2500 ISO and exposed that way. Also, whether he was shooting raw or a codec that bakes in the ISO. The specific camera used would make a big difference in the results. 

It appears to me that the second image of the kid in the car has a vignette and possibly some power windows applied. Personally, I’ve found it difficult to say what’s a result of the in-camera exposure, post-processing, or the grade on a finished image. 

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1 minute ago, Max Field said:

Could it have something to do with how dynamic range in the highlights/shadows shifts depending on where the ISO is placed? 2500iso will get a different spread than 200 iso according to these charts I've seen

Yes, I think the reason for ‘why’ is pretty clear,  to capture more stops of detail in the highlights and avoid clipping at all costs.

The question is then how to still achieve relatively clean shadows and nuance in the few remaining stops in the lower tones.

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5 hours ago, Satsuki Murashige said:

I don’t have any specific info but if I had to guess what ‘dynamic range remapping’ means, I would assume that it’s just applying a custom gamma curve to the log footage before doing the Rec.709 transform to accommodate the extreme underexposure. Probably a big lift of the mids and shadows combined with chroma denoising?

It’s not totally clear whether the DP just rated the camera at 2500 EI and while recording at the native ISO and did the push in post, or actually set the camera to 2500 ISO and exposed that way. Also, whether he was shooting raw or a codec that bakes in the ISO. The specific camera used would make a big difference in the results. 

It appears to me that the second image of the kid in the car has a vignette and possibly some power windows applied. Personally, I’ve found it difficult to say what’s a result of the in-camera exposure, post-processing, or the grade on a finished image. 

I feel a lot of this was achieved in the grade but definitely think he'd have had to shoot for it on the day. Camera was Alexa Mini.

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There's an excellent article somewhere on the cinematography of Atlanta, which I believe uses a similar technique. I worked as an AC on a feature where the DP would use the Alexa at 1600 ISO or 3200 ISO to get more of a gritty image (and better highlight detail), but I think on Atlanta they shoot at 800 ISO with custom viewing LUTs that push a couple stops, then then use those LUTs as the basis of the grade or a reference instead.

Brandon Trost I believe used to rate the Red MX sensor a couple stops brighter than it really is and push in post for a similar effect, but I believe Red is metadata and Arri ProRes is not so there's some logic behind shooting at 800 ISO and rating at 2500 ISO.

I wouldn't know what it is.

In practice, it might not matter why. Someone already figured out something that works. Shoot with the Alexa at 800 ISO, underexpose by a stop and two thirds, push the image by a stop and two thirds in the grade.

Edited by M Joel W
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5 hours ago, AJ Young said:

I tested this thought of dynamic range remapping, aka redistribution! Here's my results:

http://www.ajyoungdp.com/articles/blog/OverUnder01/

http://www.ajyoungdp.com/articles/blog/TWC_underexposure/

Hope these help!

This was a GREAT read, AJ. Thank you so much for sharing. 

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1 hour ago, M Joel W said:

There's an excellent article somewhere on the cinematography of Atlanta, which I believe uses a similar technique. I worked as an AC on a feature where the DP would use the Alexa at 1600 ISO or 3200 ISO to get more of a gritty image (and better highlight detail), but I think on Atlanta they shoot at 800 ISO with custom viewing LUTs that push a couple stops, then then use those LUTs as the basis of the grade or a reference instead.

Brandon Trost I believe used to rate the Red MX sensor a couple stops brighter than it really is and push in post for a similar effect, but I believe Red is metadata and Arri ProRes is not so there's some logic behind shooting at 800 ISO and rating at 2500 ISO.

I wouldn't know what it is.

In practice, it might not matter why. Someone already figured out something that works. Shoot with the Alexa at 800 ISO, underexpose by a stop and two thirds, push the image by a stop and two thirds in the grade.

Interesting! I think this may be the article here. Definitely an intriguing creative choice to experiment with.

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17 hours ago, AJ Young said:

You can do it via overexposure as well! John Seale did it for Mad Max: Fury Road on their day for night sequences. Source

You can indeed do it both ways. The technique of deliberately under or overexposing to move your picture information up or down the characteristic curve, in order to best utilize the available dynamic range is as old as photography itself. In black & white photography, in particular, you’ll often hear photographers talking about what speed they rate their favorite stocks. Ansel Adam’s famed zone system and development technique was all about placing exposures to maximize shadow detail, then processing to favor highlights. This is not a new idea. It’s just rather amusing that it’s now being called “dynamic range remapping”.

It sounds a lot like something that an online photography journal like FStoppers might come up with. A writer with a deadline for an article but no idea what to write about, takes a well known technique, gives it a new, technical sounding name, knocks out 1000 words, and then publishes it, probably with a clickbait headline like “The Photo Technique You Absolutely Must Know!

To the OP, both pics are simply underexposed. In the second pic, it appears to have been done for mood. You can see from the sky behind the car that it's after sunset, so it would make sense that the picture has been exposed a little under to convey the feeling of fading light. In the first picture, it looks as if it has been underexposed in order to maintain detail in the hot exterior, letting the person in the doorway go dark, presumably with the intention of lifting the shadows in post to regain some detail there, which is a common thing to do. In this particular shot, it's extreme enough to wonder if they've actually done that, because her face has almost no detail in it, but if this is from a finished piece, then it's obviously artistic intent. As I've said, over or underexposing to prioritize shadows or highlights is as old as photography, and it's fundamentally very simple. Don't get confused by made-up technical jargon.

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Ansel Adams proceded under the belief that all the latitude for film was in the highlights, hence why he usually exposed for the shadow detail he wanted to capture and then developed for the highlight detail he wanted to retain.  Digital is the opposite, most of the latitude is in the shadows because of the abrupt clip above a certain level of overexposure. It's one reason why when I shoot digital stills, I often rate the camera at a low ISO and then expose for the brightest thing in the frame and then bring up the shadows in post. 

Or I set the exposure compensation to always underexpose a certain amount if I have to work with auto settings -- sometimes for street photography, I pick an optimal shutter speed and f-stop for action and set the ISO to Auto with exposure compensation set for -0.7.

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OP, do you want to extend the range? Is the photo shown supposed to be good or bad? 

Anyway, if you are talking about extending the range, you HDR it. If you just want something printed down, then do it in post.

HDR example

NSFW

An example of what 2-1/2 hours of Lightroom can do for a photograph. – Daniel D. Teoli Jr. (wordpress.com)

I don't fool with changing ISO, I just know if something is underexposed a stop or two and push it with the PP. 

Below is a project where you could not shoot normal and everything had to be pushed a couple stops or more for the night shots. I pre-tested some shots to know my limits of underexposure, but with candid work in low light you sometimes can't abide by limits. That is the hallmark of the expert documentary cameraman...they work with what they got and bring home the goods. Beside pushing the night shots, many of the day photos are lightly HDR'd.

NSFW

De Wallen: Amsterdam’s Red Light District – Expanded Preview – Daniel D. Teoli Jr. (wordpress.com)

An example of push processing a digital image. – Daniel D. Teoli Jr. (wordpress.com)

Now, you are not going to produce perfect photos taken while walking, from the hip, guesstimating exposure, zone focusing in a local where photography is banned. You either make it work in post or it is trash. If you are a tripod shooter, and can reshoot and do tons of tests, then sure you can hopefully get the perfect image you are after.

Edited by Daniel D. Teoli Jr.
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