Mystery Box is pleased to announce updates to its HDR Utility LUTs, to take advantage of our new Gen2|HDR™ color science. These LUTs were updated for a public release on the Mystery Box web store on September 14th, and are immediately available.
Since we released our previous version of our HDR Utility LUTs, we’ve encountered a number of other questions or problems in HDR that can be resolved through look-up tables. Additionally, we’ve developed and established our Gen2|HDR color science and workflows, and have created tools for working within this new paradigm.
The new problems addressed:
- BRIGHTNESS & CONTRAST OPERATIONS ARE NOT OPTIMIZED FOR HDR - They're optimized for linear or gamma encoded images. How do we better work with them in HDR?
- SDR & HLG HAVE STANDARD CONTRASTS, PQ DOES NOT - Moving from camera log into PQ needs to be consistent across camera systems.
- HLG HDR INCORPORATES A SYSTEM GAMMA THAT AFFECTS IMAGE BRIGHTNESS AND DYNAMIC RANGE - Moving between calibrations adjust brightness and affects contrast.
- IT'S OFTEN NECESSARY TO RESTRICT COLOR SPACE OR DYNAMIC RANGE - Containers are bigger than displays, so how do we add limits to our signal?
- S-LOG3 IS AN ESSENTIAL HDR MEDIUM, ESPECIALLY IN BROADCAST - What tools do we have to move in or out of S-Log3?
- REC. 709 AND REC. 2020NC TRANSFER MATRICES ARE INCOMPATIBLE - How do we fix color errors introduced by bad matrix transformations?
Because of the way that images have been recorded up to this point, the existing methods for adjusting brightness and contrast have less predictable results in HDR.
In SDR gamma encoding, or in a linear context, brightness, or gain, operations tend to push the brightest parts of the image up more quickly than the darks. When the same math is applied to HDR images, however, one of two things happen (depending on how the application is representing the data): the brights jump up in maximum value exponentially faster than the mids and the lows, or the mids and darks jump up substantially faster than the brights.
Similarly, in HDR the standard contrast adjustments tend to push the darks substantially dark and more contrasty than the brights, or push the brights into impossible bright ranges without much finesse.
While it’s possible to manually adjust and correct for both situations, it adds additional steps and ambiguity to the color correction and mastering process.
Further, the traditional tools of adjusting brightness and contrast fundamentally require fixed reference black and white points within an image, which is not a concept prescribed by HDR, and is at odds with Gen2|HDR thinking, where the image is independent of the medium.
Mystery Box has prepared three LUT packs focused exclusively on brightness and contrast operations within a Gen2|HDR context.
Devising a solution for applying contrast to an HDR image led us to the core concept behind Gen2|HDR thinking. As such, more details will come in the future about how the solution works. As it turns out, the same solution for adding uniform contrast to HDR images solves two other problems: HLG System Gamma Display Calibrations, and the lack of a standard contrast in PQ. As such, the two LUT packs with solutions for contrast will be presented in a moment.
Traditional brightness or gain operations are designed to adjust the overall image exposure values, and in an ideal world these would be uniform across every stop of dynamic range.
To this effect, we’ve prepared the HDR Exposure Value Adjustment LUTs, which replaces the HDR10 Nits Adjustments LUTs. These new LUTs adjust the exposure value of a PQ or HLG HDR image up or down by a specific amount, while maintaining image contrast. The following values are included for both PQ and HLG HDR:
Additionally, PQ includes a ±3.32 and HLG includes a ±3.58 EV. These represent a bidirectional move from specific output values. For PQ, this is a move from 100 to 1,000 nits, or from 1,000 to 10,000 nits. For HLG, this is a move from x 1 to x 12 peak output reference (or vice versa).
More specifics on equating exposure values to linear light is provided in the notes for the LUT pack.
Imagine an SDR display directly attached to a broadcast camera, capturing a scene. Is one stop of dynamic range in front of the camera reproduced as one stop of dynamic range at the display? No.
SDR systems, along with film systems before them, stretch the dynamic range in a predictable way, that adds contrast to the recreated image. In SDR systems, that stretch factor was 1.09: each stop of dynamic range input becomes 1.09 stops of dynamic range at the display. This standard contrast, or stretch, is so ‘normal’ that viewing any image without it appears washed out.
Both SDR and HLG HDR have a stretch factor, more officially termed an OOTF, or system gamma. PQ HDR does not.
Mystery Box has prepared a set of LUTs for uniformly applying contrast in PQ HDR. Using the concept of an OOTF, uniform stretch factors can be applied to LOG images converted into PQ space.
These stretch operations are fixed at three different values: 100 nits, 1000 nits, and 10,000 nits. Any brightness value above the fixed value will be stretched upwards, while any brightness value below the fixed value will be stretched downwards. 12 stretch factors are included for each fixed value, from 0.90 to 1.40 in 0.05 increments (1.00 excluded), 1.50 & 1.60. Values less than 1.00 flatten the image, while values greater than 1.00 increase the image contrast. Standard contrast is approximated with the OOTF of 1.10.
In addition to the new PQ HDR Add OOTF (Add Contrast) LUT pack, standard contrasts have been added to the camera LOG conversion packs, with Low, Standard, Medium, High, and Very High variants added to the various LOG format to HDR conversion packs.
The Hybrid Log Gamma specifications provide for an adjustable system gamma and any number of maximum brightness values. While the system gamma value is intended for calibration, it’s also used within the specification to determine the dynamic range of the output video system.
While ITU-R Recommendation BT.2100 defines a standardized implementation of Hybrid Log Gamma (1000 nits peak, with a system gamma 1.2), this may not be applied to all grading monitors. The mastered image will then look different on all other HLG monitors.
Mystery Box has prepared a set of HLG monitoring or mastering LUTs that can be applied to HLG content to precompensate for the display’s calibrated system gamma. For instance, if the display is applying a system gamma of 1.4, the colorist may apply a non-rendering monitoring LUT that precompensates for system gamma 1.4 by dividing it out of the output image signal. The colorist could then color correct as usual, confident that their display is not substantially altering the contrast they apply to the image.
During color correction, the colorist may apply a “Remove HLG System Gamma Display Precompensation” LUT to add contrast to the image, these having the equivalent function of adding an OOTF in PQ HDR, as described above.
Or, if a colorist is adapting HLG content mastered with one system gamma, and is looking to restore the original artistic intent on a display with a different system gamma, they may first apply a “Remove HLG System Gamma Display Precompensation”, then apply an “Add HLG System Gamma Display Precompensation” to match a target HLG system.
NOTE: Because of the many issues with scene referral in Hybrid Log Gamma HDR, Mystery Box recommends against its use in feature film production or HDR mastery. However, we have still prepared and provided the same brightness and contrast tools we’ve prepared for PQ.
The Rec. 2020 color space is the standard for television display systems, but there is no display, on the market capable of reproducing 100% of Rec. 2020. Similarly, there is no commercially available display that can cover all of PQ HDR’s 26 stops of dynamic range, with 10,000 nits peak.
Mystery Box has prepared color space and dynamic range clamps that can be applied to restrict brightness values outside of a specific range, or restrict wide color spaces to colors found only in smaller color spaces.
For instance, when grading on a Sony BVMX300 operating in Rec. 2020 mode, a colorist may find it useful to add a P3 D65 color space clamp, allowing the signal to contain only the same colors the monitor is capable of displaying. Or, they may choose to apply a 1000 nits high clipping LUT that ensures that the signal does not contain any brightness values above what the display is capable of showing.
In both of these cases, applying the clamp or clipping LUTs ensure that the image as it’s seen in color correction never suddenly looks different on newer technologies that can display values beyond those on the monitor used for grading.
Low clipping LUTs are provided for the same reason, as well as to add a clipping point above what the display is capable of reproducing to reduce the effect of the noise floor or for other creative reasons. As such, in addition to adding a straight clip, Mystery Box has prepared low clipping LUTs that crush values below the targeted value to “code 0” black.
The color space clamps are now included in the HDR Application LUTs pack. The PQ clipping LUTs are provided in their own LUT pack. Note that because of how the HLG standard works, it’s not possible to create clipping LUTs with any predictable results.
S-Log3 is quickly becoming the third HDR medium, especially in broadcast acquisition, where it may be paired with Rec. 2020 or S-Gamut3 color primaries as the primary means of capturing HDR content for broadcast. However, it is not a delivery format, and not all cameras shoot in S-Log3.
Mystery Box has created a LUT pack with S-Log3 LUTs for broadcasters, allowing them to move S-Log3 into PQ or HLG HDR, including S-Gamut3 transformations if desired. Additionally, we’ve prepared LUTs that move existing PQ or HLG content back into S-Log3, allowing broadcasters to mix asset sources in a combined S-Log3 pipeline.
To help broadcasters to work in HDR, we’ve prepared a new Utility LUT pack comprised of all of our LUTs that would be useful in broadcast applications, including the Sony S-Gamut3 S-Log3 Broadcaster’s Pack, our HDR to SDR conversion LUTs, our SDR to HDR conversion LUTs, HDR & SDR color Primary Conversion LUTs, PQ & HLG Cross Conversion LUTs, and our PQ HDR Add OOTF (Add Contrast) LUTs. These are all suitable for real-time application and the real time mixing of content sources, giving broadcasters new tools for faster HDR adoption.
The Rec. 709 RGB to YCbCr Transfer Matrix and the Rec. 2020 RGB to YCbCr Transfer Matrix (Non Constant) yield different YCbCr values when moving from RGB to YCbCr, and yield different RGB values when moving from YCbCr to RGB. This results in color shifts within improperly decoded footage.
Additionally, SDI interfaces are set up to always use the Rec. 709 transfer matrix, while most televisions (especially those using HDR metadata injection) decode the transfer matrix as Rec. 2020.
Mystery Box has prepared two LUTs that may be applied as mastering or monitor LUTs to correct for improper decoding or encoding of the transfer matrix.
These two LUTs are included in the updated HDR Application LUTs pack and are labeled “MBOX Fix for Rec709 Matrix Decoded as Rec2020nc” and “MBOX Fix for Rec2020nc Matrix Decoded as Rec709”
Examples of cases when these LUTs should be used (and how to fix them):
Display is set to BT.2020NC matrix, but the signal is BT.709 matrix
CONTENT IS UNGRADED
Apply Fix for Rec709 decoded as Rec2020nc as a non-rendering monitoring LUT
CONTENT IS ALREADY GRADED
Apply Fix for Rec2020NC decoded as Rec709 as an input LUT on previously rendered footage or as an output LUT on a timeline to be rendered.
Content is encoded using Rec2020NC transfer matrix, but decoded in an application that ignores color primaries and transfer matrix metadata (ex: After Effects)
Apply Fix for Rec.2020 NC Decoded as Rec 709 within the application, or after rendering
HDR to SDR Conversion LUTs - New in Version 1.1
Added HLG to SDR and P3D65 PQ to SDR conversion LUTs, using the same color science as the HDR10 to SDR LUTs
Added an HDR10 to SDR reversible LUT, with corresponding SDR to HDR10 transformation
Renamed pack to HDR to SDR Conversion LUTs to correspond with updated content
HDR & SDR Color Primaries Conversion LUTs - New in Version 1.1
Added color space transformations for Hybrid Log Gamma
Renamed the HDR10 LUTs to PQ (HDR10)
HDR Exposure Value Adjustments - New in Version 1.1
Renamed all LUTs to move away from a Nits relationship to more accurate Exposure Values
Increased the granularity of EV adjustments
Added EV adjustments for HLG HDR, in addition to PQ HDR
Renamed LUT pack to reflect focus on Exposure Values
PQ & HLG Cross Conversion LUTs - New In Version 2.0
Updated LUTs to be fully reversible, and visually perfect when moving to or from BT2100 HLG.
Included two reversible “artistic” conversions that allow for different transfer characteristics, with respect to contrast and highlight compression
Added PQ to HLG conversions for alternate HLG System Gammas than the BT.2100 SG 1.2.
Renamed the LUT pack to reflect broader PQ HDR Compatibility
HDR Application LUTs - 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
PQ to HLG HDR Advanced Conversions v1.0 - NEW
A LUT pack to move from non-standard PQ brightness values into HLG HDR, allowing the operator to assign a specific PQ nits value to the HLG reference value. These are for advanced conversions, especially when the PQ range exceeds a 1000 nits peak, and are not recommended for average users.
PQ Add OOTF (Add Contrast) v1.0 - NEW
A LUT pack to add a stretch factor / contrast to PQ HDR signals. These compensate for the fact that unlike SDR and HLG, the display in a PQ HDR system (HDR10, Dolby Vision) does not add any contrast: the signal is display referred. Any content translated directly into PQ will lack the standard contrast appearance found in SDR and HLG: these LUTs add the contrast (OOTF) that’s missing, and extend the dynamic range of the content to a more normalized display dynamic range.
A LUT pack to clip PQ graded footage a specific low or high nits values. These ensure that no data exceeds what you can see on the screen, or to ensure that you produce content with the cleanest black levels. 1D and 3D versions fo the LUTs are included.
A LUT pack to help manage the ambiguities of HLG System Gammas. These LUTs will add display precompensation (FLATTEN the image) so that when the display adds its SG, the image will retain its originally intended contrast, or remove display precompesation (ADD CONTRAST) to compensate for the fact that your HLG grading display is adding contrast to what you’re seeing, in effect baking in your contrast to the HLG signal. These may also be used to add a target HLG OOTF.
Sony S-Gamut3 S-Log3 HDR Broadcast LUTs v1.0 - NEW
A LUT pack to manage HDR data to and from Sony S-Gamut3 & Sony S-Log3, including S-Log3 with BT.2020 color primaries. Intended for use in a Broadcast environment, where S-Log3 may be a transmitted HDR acquisition or intermediate format, or to conform to PQ or HLG HDR from S-Log3 for broadcast.
Simple Grading HDR Utility LUTs v1.0 - NEW
A collection of simplified LUT packs, suitable for anyone working in HDR. Mystery Box recommends these LUTs as the base LUTs for anyone working in HDR.
Broadcaster’s HDR Utility LUTs v1.0 - NEW
A collection of fully featured LUT packs for Broadcasters who need to incorporate HDR into their broadcast pipelines. Mystery Box recommends these LUTs as the base LUTs needed to adapt existing broadcast pipelines to HDR capable with minimal time and investment costs, and for simultaneous broadcast in SDR, PQ, and HLG.
Complete HDR Utility LUTs - New In Version 2.0
All LUT packs updated to the latest versions
Added the five new HDR Utility LUT packs to the collection (PQ to HLG Advanced Conversions, PQ Add OOTF, PQ Hard Clipping LUTs, HLG Add & Remove System Gamma Display Precompensation, Sony S-Gamut3 S-Log3 HDR Broadcast LUTs)
Panasonic GH5S HDR10 LUTs - New In Version 1.1
- Added v2 GH5S to BT2020 PQ Grading LUTs based on Mystery Box’s Gen2|HDR Color Science
- Added GH5S HLG to PQ HDR conversion
Panasonic V-Gamut V-Log HDR Camera Pack - New in Version 2.0
- Updated to include Mystery Box’s Gen2|HDR Color Science
- Added V-Log to PQ HDR transforms, combined with V-Gamut to Rec. 2020 transformations
- Added V-Log to PQ HDR (-1.5 EV) variants
Phantom Cine LOG HDR Camera Pack - New In Version 2.0
- Updated to include Mystery Box’s Gen2|HDR Color Science
RED RedWideGamutRGB Log3G10 HDR Camera Pack - New In Version 2.0
Updated to include Mystery Box’s Gen2|HDR Color Science
Added Log3G10 to HDR and combined RedWideGamutRGB Log3G10 to Rec.2020 PQ conversion LUTs
Sony S-Gamut3 S-Log3 HDR Camera Pack v1.0 - NEW
A LUT pack for moving from S-Gamut3 / S-Gamut3.cine S-Log3 footage into PQ HDR grading space, using Mystery Box’s Gen2|HDR Color Science
Complete Camera HDR LUTs - New in Version 1.1
All LUT packs updated to the latest versions to include Mystery Box’s Gen2|HDR Color Science
Added Sony S-Gamut3 S-Log3 HDR Camera Pack
Written by Samuel Bilodeau, Head of Technology and Post Production