HDR Application LUTs v 1.1
HDR Application LUTs v 1.1
New In Version 1.1
Added Fixes for Rec. 709 & Rec. 2020 RGB to YCbCr transfer matrix errors
Added Full to Legal and Legal to Full scaling LUTs
Added Color Space Clamps to allow for restricting wider color spaces to color values valid in smaller color spaces
The Mystery Box HDR Application LUTs are LUTs that make it easier to handle some of the technical aspects of grading in HDR.
There are seventeen LUTs in this pack:
MBOX Adobe Limited HDR to ST2084
MBOX Fix for Rec709 Matrix Decoded as Rec2020nc
MBOX Fix for Rec2020nc Matrix Decoded as Rec709
MBOX Full to Legal
MBOX Legal to Full
MBOX HDR10 1000 Nits Hard Clip
MBOX HDR10 4000 Nits Hard Clip
MBOX ST2084 HDR10 Output Grading Curve
3 x Color Space Clamps for restricting P3. D65 to valid Rec. 709 legal colors (HLG, PQ, SDR)
3 x Color Space Clamps for restricting Rec. 2020 to valid P3 D65 legal colors (HLG, PQ, SDR)
3 x Color Space Clamps for restricting Rec. 2020 to valid Rec. 709 legal colors (HLG, PQ, SDR)
The 1000 and 4000 nits hard clip LUTs force a hard clip at 1000 and 4000 nits respectively, to ensure you are not storing additional 'unseen' details in the whites when grading on the Sony BVM-X300 and Dolby Pulsar HDR Reference Displays.
The Adobe Limited HDR to ST2084 allows you to scale the contrast of images processed using Adobe Photoshop and output as an Rec. 2020 ST.2084 image into a much larger brightness range, to circumvent Adobe's forced process of limiting HDR values to SDR brightness ranges.
The Full to Legal and Legal to Full LUTs scale the data range of encoded content to correct for any discrepancies in how it was encoded or stored. These are useful for SDR as well as for HDR
The "Fix for Rec709 Matrix Decoded as Rec2020nc" and "Fix for Rec2020nc Matrix Decoded as Rec709" corrects for improperly decoded or improperly flagged YCbCr Matrix Coefficients. Since the RGB -> YCbCr math is different under Rec. 709 and Rec. 2020, it's important that when reversing the transform (YCbCr) the correct coefficients are used.
Some applications always use the Rec. 709 Matrix Coefficients, even when the content was encoded using Rec. 2020nc Coefficients and is properly flagged. The "Fix for Rec2020nc Matrix Decoded as Rec709" provides a corrective fix, primarily in the blues and blue-greens. On the other hand, many HDR displays allow for the selection of the matrix coefficients at the display, while many color correction software applications will only use the Rec. 709 coefficients for the SDI output, even when the working color space is Rec. 2020. The "Fix for Rec709 Matrix Decoded as Rec2020nc" provides a fix so that the encoded files match what was seen on the display.
The MBOX Color Space Clamps are designed to limit a wider color space to a more limited color space, such as a limit to only legal P3 D65 values when working in Rec. 2020, while taking into account the transfer function used for grading / encoding. The "MBOX Clamp Rec2020 to P3 D65 Color (PQ)" LUT, for instance, prevents any RGB using Rec. 2020 primaries from exceeding the legal P3 D65 range, when working in PQ HDR. Clamps for P3 D65 and Rec. 709 are provided for Rec. 2020, and clamps for Rec. 709 are provided for P3 D65, for HDR PQ, HDR HLG, and SDR/Linear transfer functions.
The last grading utility LUT is our ST2084 HDR10 Output Curve that we use in DaVinci Resolve to compress the highlights and expand the darks as we apply a gain function, which allows traditional Lift, Gamma, and Gain adjustments to behave more evenly in HDR. For a full discussion as to why that is, see our post HDR Video Part 5: Grading, Mastering, and Delivering HDR. Note that we feel it’s better to apply this curve as a bezier curve in DaVinci resolve, as it offers fine tuning for the feel, and allows the curve to extend into out of range data.
For a demonstration of how the LUTs work and the problems they solve, visit our blog post here.
These LUTs are licensed for use in a post-production setting for applying to assets prior to the assets distribution. If you are interested in incorporating these LUTs into HDR encoding, distribution, or exhibition technology, please contact us for more information on licensing.