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BT2020 or P3-D65


Jon Pais
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This is an excerpt. For the full post, click here.

“If you want to use an OLED for HDR mastering, I highly recommend using P3-D65 as your working color space. That’s the best choice in such pipelines. Don’t use BT.2020 with an OLED, only BT.2020 limited to P3-D65. I see this mistake all the time.” – How to choose an HDR Monitor for Color Grading, Tim Yemmax, Colorist

Colorists are virtually unanimous in recommending BT.2020 (P3-D65 limited) for grading HDR content and for good reason: DCI-P3 happens to be the color gamut most widely used by the film industry; Netflix requires deliverables be P3-D65 ST.2084; reference monitors in post-production houses support the full P3 color space; and even ubiquitous mobile devices support as much as 99% of the P3 gamut. In fact, it would be no exaggeration to point out that billions of people are carrying in their pockets a display with greater color accuracy and higher brightness than those found on the sets of most multi-million dollar productions. It goes without saying, however, that few colorists regularly upload anything but tutorials to YouTube; that precious few have ever uploaded a single HDR video in their life; and that relatively few colorists have any experience at all grading HDR professionally; furthermore, it’s no secret that not a few are even openly hostile toward high dynamic range video. We only bring this up because it may help to explain colorists’ stunned disbelief upon learning that on Google’s own YouTube help page, using the P3 color space is strongly discouraged. Curiously, neither on his English language YouTube channel nor on his German language one does Tim Yemmax recommend P3-D65 in his otherwise excellent tutorials – even though video monitoring settings, color processing modes and a calibrated display are all mutually interdependent and need to match for accurate results.

Numerous thoughts passed through our minds when we decided to embark on this undertaking. Initially, we thought it might be entertaining to conduct an online experiment to see whether anyone apart from a seasoned professional like Tim Yemmax could also instantly recognize when a YouTube video was carelessly graded in BT.2020 instead of the industry standard P3-D65. Naturally, we’d want to upload a few videos to YouTube to discover whether the color shifts were real – but how? And perhaps most importantly of all, would switching to P3-D65 help revitalize our waning YouTube subscriber base? 

Acquisition Format

Any serious discussion of color spaces must surely consider the acquisition format. That is, if the color processing mode is going to be P3-D65, would we be better off recording a smaller color space like S-Gamut3.cine? Or should we instead be capturing the widest available gamut – S-Gamut3 – thereby preserving as much of the sensor’s native color space as possible and future-proofing our timeless masterpieces of cinematic art for posterity? Dolby weighs in:

“Where content is going to be color graded, it is recommended to use source material that best retains the native color gamut and original dynamic range of the content at the time of its origination in order to create high quality Dolby Vision content. 

Where content will be directly edited and then aired with just some minor color corrections or even without a color grading process, capturing in a format that matches to the color gamut and dynamic range of the delivery requirements can enable a simpler workflow”. – Dolby Vision

S-Gamut3 it is then. Or, so you’d think: S-Gamut3.cine still enjoys the greatest popularity among Sony shooters.

Hardware

When it comes to grading, the very first requirement is inarguably a mastering monitor large enough to assess UHD image quality at a viewing distance of 1.5 times picture height (a rule of thumb is the smaller the monitor, the better things look – and only when they’re really bad do problems become apparent) and capable of being calibrated to Rec.2020 PQ P3-D65. “That’s child’s play,” you’re probably thinking, “just adjust the settings on the LG CX!” That there is a hidden menu on the LG CX with Colorimetry, EOTF, Mastering Peak and Mastering Color, MaxCLL and MaxFALL, P3-D65, Rec.2020 as well as various flavors of SDR goes to show just how wildly popular LG OLEDs have become among both colorists and filmmakers, but information about how exactly to configure the settings is all but non-existent and we found that changing the colorimetry or the mastering color had no discernible affect on the picture whatsoever.

Not only that, but regardless of whether HDR Rec.2020 PQ or Rec.2020 PQ P3-D65 were selected on the color management page of Resolve, our TV obstinately detected BT.2020 as the incoming signal.

While the LG CX display itself is said to cover as much as 96% of the P3 gamut, apparently the HDMI protocol doesn’t technically support using P3 color primaries – which must be what the warning on the YouTube help page is referring to when it says that P3-D65 is not a supported format for delivery to consumer electronics. That being the case, in order to make the display compliant with other color spaces, you’ll need to invest an additional $1,295.00 into something like the Teranex Mini SDI to HDMI 8K ($1,600.00 here in Vietnam). So, we’re looking at a total expenditure of around $4,000.00 including an LG OLED TV and UltraStudio 4K Mini HDR with Thunderbolt 3 – all for a non-monetized YouTube channel with fewer than fifteen hundred subscribers of whom only 7% watch our content on a regular basis! 

According to Ted Aspiotis, “The P3D65 selection in the HDMI Override menu is just a cosmetic option; it’s the same as REC.2020. LG hasn’t enabled it yet, and it’s pending to be enabled in the future (or never, as its over two years of waiting already)”.

Tyler Pruitt adds, “You can calibrate the TV to HDR 2084 P3 gamut using Calman. A lot of facilities are doing this and usually they do one picture mode, say HDR cinema mode to 2020 HDR, And a second HDR picture mode like HDR Filmmaker mode to P3 HDR. This is a very common practice when using LG TVs in postproduction for HDR”. 

Evidently, there are hordes of hapless filmmakers out there who sincerely believe that they’re grading HDR Rec.2020 PQ P3-D65 – when they’re not!

 

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