Hi @guest.r,
I came across some interesting reading. I immediately thought this might be of interest to your shader. Note that the documents are from 2011, so it surpasses sRGB specification by quite some time.
SpectraCal’s Director of Software Development, Joel Barsotti, argues that the BT. 1886 gamma function (EOTF) more accurately matches legacy CRT technology than previous power law based functions. The argument is that it properly takes into account the legacy “contrast” and “brightness” controls on CRTs.
I was especially surprised by how much focus there is in the documents on matching legacy CRT monitors.
In a Calman FAQ document https://kb.portrait.com/help/bt-1886-10-questions-10-answers some of the advantages are mentioned.
BT.1886 offers several clear advantages over previous practice. First, BT.1886 more closely mimics the behavior of CRTs than previous power functions
Previous gamma functions additionally do not adequately account for independent adjustment of brightness and contrast controls on a display.
BT.1886 makes little difference at the bright end of the gray scale, but it makes a substantial difference at the black end.
Note these documents are from 2011, so are surpassing the sRGB spec / considered a worthwhile improvement on sRGB EOTF.
If you’re interested, please see Annex 1 on page 2 and Appendix 1 (Informative) EOTF-CRT matching on page 3 of the ITU recommendation document: https://www.itu.int/dms_pubrec/itu-r/rec/bt/R-REC-BT.1886-0-201103-I!!PDF-E.pdf
For the shader I was especially triggered by the comments in Appendix 1 (Informative) EOTF-CRT matching, which focuses on matching a CRT for which you know (or can measure) the black level and brightness level:
The EOTF specified in Annex 1 is considered to be a satisfactory, but not exact, match to the
characteristic of an actual CRT. When it is desired to match a CRT, the Lw and LB parameters of the
EOTF can be set to the corresponding values of the CRT that are being matched.
Do you think that this BT. 1886 implementation of contrast and brightness control directly with the EOTF could improve on the current brightness and contrast controls in the shader?
EDIT: In appendix 2 there’s also the noteworthy comment:
In measuring the EOTF of a large number of CRTs it was determined that the EOTF of the
CRT was in fact highly variable when the brightness/contrast was adjusted, it is therefore not
possible to 100% emulate CRT capability (or limitations).
Users of this Recommendation in combination with the new technologies should be able to achieve
a higher degree of image presentation repeatability than that offered in the past.
