HDR and DOLBYVISION. What is it and why do I need to know?

Our Managing Director Angela Cerasi recently completed Australia’s first feature film to be graded in Dolbyvision – “Swimming for Gold” starring Peyton List.  In the following post, Angela attempts to de-techify the complex and involved process and explain why we need to know about it.

 

 

 

 

 

 

WHAT IS HDR, DOLBYVISION AND WHY YOU NEED TO KNOW

HDR (High Dynamic Range) is an expanded range of colour and brightness now available to audiences in their modern TVs and devices.  HDR-capable TVs and devices are becoming the new standard, just like when High Definition (HD) became the new standard (as opposed to Standard Definition (SD), or colour became the norm from black and white.  HDR is becoming the new standard – your new Panasonic TV will now have HDR/Dolbyvision capability and iPhones too.  Any Netflix Original Series commissioned from now on will most likely require an HDR or Dolbyvision deliverable.

Up to now, colourists have mostly worked in a colour range called Rec 709.  Brightness has been restricted to 0-100nits (nits = a measure of luminance).  With HDR finishing, there is at least 1000nits of brightness available, this is ten times as bright!  The idea is that technology is improving all the time to portray more realistic images with higher contrast, darker darks and brighter brights.  In real life, outside in the sun the brightness level might be 9000 nits for example.  The technology is being engineered as we speak to get consumer TV’s to replicate this level.  It’s actually hard to imagine what this would look like – real life in a TV set.  For now, Angela had a chance to play with 1000 nits, and that in itself was absolutely gobsmacking.

 

(BT.709 shows the current colour volume we have to play within in Rec 709, BT.2020 shows the colour volume capable in HDR)

 

Colour grading HDR has the scope to push everything you thought was possible even further.  Bluer deeper blues, twisting reds through every shade of orange red to pink red, sparkling diamond whites, many shades of inky darkness.  And when you “push” the colour or brightness the image doesn’t break up, it doesn’t feel like there is a limit, it is the most fun a colourist can have in a modern day grade (in Angela’s opinion!)  The storytelling capability is immense, with the image feeling more alive and vivid you can immerse the audience, surprise and delight them, you have the potential to really track an emotional arc of a story through where you sit the exposure of a scene.

By the way, it is worth noting here that HDR for film and video is not the same as “high dynamic range photography,” which is about processing an image by blending different exposures – the goal being to capture both the brightest and darkest parts in to a frame.

“Dolbyvision” is a word created by the global audio visual company Dolby which refers to their own HDR technology.  The industry standard of HDR is called HDR10+ and this format is free for manufacturers of TVs and monitors to use.  Dolby Vision on the other hand, requires the manufacturer to pay a licence fee.  Colour scientists and Dolby engineers have been working on this technology for years and there are several reasons why Dolby claims Dolbyvision is the premium HDR experience.

Before diving in to these, it is interesting to know that there are currently only 5 post-production houses in Australia which are certified to finish in Dolbyvision, and globally there are only 138.  To set your post-production house up for Dolbyvision you require a (currently very expensive) Dolbyvision broadcast monitor, training, a license and certification from a Dolby Engineer.  It is an expensive investment but no doubt one that we will see spreading more quickly and rapidly throughout our industry as it becomes the new standard.

 

HOW DOLBYVISION WORKS

Ok, so this is a simplified version of a very complex workflow.  I have tried to unpack and use analogies where possible so stay with me!

So in order to create a project in Dolbyvision, film cameras must capture data in HDR (high dynamic range) in production.  If the camera is shooting LOG (the Logarithmic curve where your image looks washed out and milky) and at least 12bit 4:4:4 (12 bits of information in each pixel), then you are shooting in HDR.  Just to give you an idea of how much information that is, in HD there are 1920 x 1080 pixels (2,073,600 pixels, each pixel with 12 bits of info stored in it).  4K is four times this many pixels, and 8K is 16 times this many pixels!!

Currently you can not view the HDR image you are capturing on your film camera on set (there are no HDR on-set monitors) so this is an issue for cinematographers trying to light for HDR and see what they are getting.  To light for HDR, the cinematographer needs to understand lighting contrast and the exposure level in different parts of the frame.  They need to know how many stops (exposure increments) the camera is capturing and where to set the exposure (the middle “stop”).

Once you have shot the production in HDR, you edit as normal.  Your editor may create (transcode) proxies to work with (a duplicate timecoded-version of the original media in low resolution) so the computer is quicker to respond when changing and moving things around all the time.

The usual conform process happens now.  This is preparing it for the colour grade and moving it from the editing software to the colour grading software.  The colourist requires the final edit in HDR so the conform artist will make sure that each proxy (like the actor’s stand-in) is replaced with the proper media (the actor).  This general explanation of the edit and conform process is the same no matter if it is Dolbyvision or not.

The difference between HDR grading and Dolbyvision grading starts here.  To colour grade in Dolbyvision you require a Dolbyvision enabled monitor, a license in your colour grading software and then you need to create a Dolbyvision master grade.

From this master grade, various “downstream” (lesser quality) deliverables can be created through automated “mapping” of the original master.  This means that the original master file (ie. graded HDR Quicktime movie) is analysed, interpolated and converted into a file for the “downstream” target device you specify (ie. HD TV display).  The “mapping” analyses each shot separately and the metadata (the DNA) it pulls from each shot is written in to an XML file.  After this automated mapping, you can then watch the target device’s version of the grade ie. the HDTV version.  It will never look as good as the HDR graded master, because this has a superior range and tones of colours and luminosity.

Just say this Dolbyvision master grade is the chocolate cake, the key difference that Dolby promotes is the amazing analysing process, the creation of an XML (recipe) and MXF (cake mix), and the ability for your Dolbyvision enabled device at home to put the correct recipe and cake mix together to create that exact chocolate cake that was concocted in the grade suite.

With HDR10 content, your HDR TV only receives basic information from the entire film or TV show (for example the cake is going to be chocolate, with butter icing and sprinkles).  Dolbyvision provides the display with updates on how each specific shot or scene should be shown (ie. the step by step recipe on ingredients and quantity and timings).  The source hits the display and gives it shot-by-shot instructions on how to portray the master grade as accurately as possible.

Dolby claims that finishing your film in Dolbyvision will mean that the image will remain looking exactly the way it was supposed too as it makes its way along the pipeline and in to the cinema, home or palms of the viewer (no matter what their device or viewing platform -as long as it is Dolbyvision enabled).

Dolby Vision allows producers to master out one file, and in it have the information required to derive both an HDR and a SDR version.  Standard HDR would require two separate deliverables, an HDR and a SDR version.

HDR grading and Dolbyvision is really exciting.  It is exciting for filmmakers who want their imagery and artistic vision to make it to the viewer looking the way in which they intended.  It is exciting for the viewer to know that they’re getting the most epic picture quality possible, the way it was meant to look.   The storytelling potential of this expanded colour and brightness is just phenomenal.  It is hard to articulate just how amazing it is.  If you run into Angela hit her up about HDR and Dolbyvision, she can’t wait to share her enthusiasm!

 

For further reading on HDR, see Alexis Van Hurkman’s great blog article: http://vanhurkman.com/wordpress/?p=3548