HLG Add & Remove System Gamma Display Precompensation v1.0

HLG Alter SG Display Precomp v1.0 - SALE.png
HLG Alter SG Display Precomp v1.0 - SALE.png
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HLG Add & Remove System Gamma Display Precompensation v1.0

150.00 300.00

The MBOX HLG Add & Remove System Gamma Display Precompensation LUTs are designed to move HLG content graded on a display with a specific system gamma, to another HLG display with a different system gamma, or to remove the system gamma all together.

There are 24 LUTs in this pack

  1. 12 x Add HLG System Gamma Display Precompensation (SGs 1.05 to 1.60, in 0.05 increments)

  2. 12 x Remove HLG System Gamma Display Precompensation (SGs 1.05 to 1.60, in 0.05 increments)

The Hybrid Log Gamma (HLG) specifications include a gamma function as part of the electro-optical transfer function that is applied at the display and converts the digital values at the display to the optical light output values.

ITU-R Recommendation BT.2100 specifies a standardized system gamma of 1.2 for broadcast applications. However, local displays may be calibrated to any number of system gammas. Color correcting in this context is fundamentally display referred, and it's not possible to guess what the corresponding scene referred digital values should be for the encoding of HLG content.

The MBOX HLG Add & Remove HLG System Gamma Display Precompensation LUTs allow colorists to remove the effect of the system gamma from the image as they perceived it, so that the contrast they observe in the color correction suite is maintained in the master file, or so that HLG OETF may be conformed to the gamma of a specific display.

The "Add System Gamma Compensation & Maintain Contrast" LUTs (HLG SG 1.0 to (DispPre) HLG SG [Gamma]) FLATTEN an HLG image such that when the DISPLAY adds the target system gamma value, the contrast is preserved. These allow for HLG OETF values to be precompensated for target display systems, so that the target displays do not adjust the image contrast.

The "Remove System Gamma Compensation & Maintain Contrast" LUTs ((Pre) HLG SG [Gamma] to HLG SG 1.0) ADD contrast to an HLG image so that the ENCODED HLG OETF file matches the authorial intent, to compensate for the HLG system gamma used on the mastering display. These are intended to create the generic HLG OETF, which can then be adapted for a large display system, such as BT.2100 System Gamma 1.2.

ALTERNATIVE USE: ADDING OOTF CONTRAST IN COLOR CORRECTION

These LUTs may also be used in conjunction by a colorist to precisely control the global applied contrast "stretch factor" when interpreting LOG data, by first applying the corresponding "Add System Gamma" LUT to match the gamma of their display as a non-rendering display LUT, then by applying the desired stretch factor from the "Remove System Gamma" LUT to the image data.

For example, if a colorist wanted to add a global contrast stretch to the image, such that each 1 stop of scene contrast is presented as 1.4 stops of image contrast, they would do the following transformation, if they were working on a BT.2100 System Gamma 1.2 display:

  • Transform the Camera LOG into HLG OETF

  • Apply the "MBOX HLG SG 1.0 to (DispPre) HLG SG 1.2" LUT as a non-rendering display LUT to precompensate for the system gamma added by the display. This will let you see the direct camera acquired image in the HLG space

  • Apply the "MBOX (DispPre) HLG SG 1.4 to HLG SG 1.0" LUT, to add a 1.4:1 stretch to each captured stop of dynamic range.

Or, to add a 1.4 stretch factor to the image WITHOUT precompensating for the BT.2100 System Gamma 1.2, simply apply the "MBOX (DispPre) HLG SG 1.15 to HLG SG 1.0" LUT, to compound the effect of the display's system gamma: 1.2 x 1.15 = 1.38 Total Gamma

For more information regarding HLG and system gammas, visit http://mysterybox.us/blog-home/ (specific content coming soon)

 

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.

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