Alister Chapman - What is HDR?

Alister Chapman gives an overview of HDR video.
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[@martin-4193]

The best explanation I ever heard so far on HDR. 👍

[@gavingreenwalt1409]

If you squeeze 14 stops down to 4 stops you don't end up with a "flat" or "log" image, you end up with a "dark" image. Log isn't HDR and HDR isn't Log. Log is just an efficient gamma to store images in. Log's only purpose is as a form of data compression, it shouldn't be thought of by anyone any differently than Zipping your word documents or 4:2:2 color. It's just a way to efficiently discard information. If Log not Rec709 was storing HDR information then there would be no reason for a camera to capture 14 stops. What most people do is they already "squeeze" 14 stops into the 6 stops of rec709 through a highlight rolloff curve and a shadow toe curve. Log (like nearly all camera curves) is just another arbitrary (but more consistently reliable) approach to squeezing HDR images into lower dynamic range video formats. The original HDR popular HDR format was EXR which is linear. If you squeeze all 14 stops onto an SDR format and apply a rec709 gamma curve it'll look extremely dark.

[@MrFreezeMovie]

There are several reasons why you are incorrect. HDR stands for "High Dynamic Range". I'd say anything over 12 stops is HDR, but that's kind of subjective. It's not a mode, or a color space. It has NOTHING to do with color! You can have a rec 709 image with 15+ stops of dynamic range! TV's now have "HDR" that can display detail in images at extended IRE values... But still you are incorrect about LOG. It certainly is "HDR" as it captures a wider range of exposures. " then there would be no reason for a camera to capture 14 stops"... clearly you don't work as a cinematographer... 14 stops isn't even enough, and is less than the most recent celluloid stocks. I said "You don't differentiate the difference between captured dynamic range and displayed dynamic range." The log image has 14 stops of dynamic range captured. Take a light meter out on set and prove this. It's maybe only being displayed at 4-8 stops. IRE does NOT directly translate to dynamic range! And the people making videos like this should know that. This is the key problem with this video. There is a MASSIVE difference between displayed dynamic range and captured dynamic range. Like I said, you need much more captured DR than displayed DR. It's why so many people are confused, and this video adds to that. There are tons of movies out there shot with an Alexa, where 14+ stops of dynamic range were used and captured in an image, and you watched it in rec 709 on an old LCD years ago.

[@neotrinity4516]

Interesting information. Can you tell me the difference between hlg and hdr10+? or are they the same thing?