BT.1886 missing in Color Management settings?

Am I missing something? I see 2.2 and 2.4 specified for gamma options, but I don’t see BT.1886 anywhere.

When you all are delivering to BT.1886, how are you monitoring? Are you just approximating it with 2.4?


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Hi,
Rec709 + 2.4 gamma is the closest to the BT1886 specifications

Rec.709+2.4 gamma is BT.1886.
As far as I understand you should not use term Rec.709 anymore when grading for HD TV, but BT.1886. Problem is that people are use to Rec.709 so much that it's hard to change.
Many companies adjusted terminology, but Resolve seams to be still in "dark ages"

It seems that there are a lot of misconceptions floating around about BT.1886.

To be clear, BT.1886 is not 2.4.

Out of 1.8, 2.2, and 2.4, 2.4 is closest to BT.1886, but it is not equivalent.

Some resources, for the curious:

http://www.spectracal.com/Documents/Whi ... T.1886.pdf

https://www.itu.int/dms_pubrec/itu-r/re ... !PDF-E.pdf

It's based on 2.4 gamma with some soft end point for black as it was designed for LCD TVs which can't reproduce proper black.
"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. For moderate black level settings, e.g. 0.1 cd/m2, setting the LB of the EOTF to 0.1 will give a satisfactory match to the CRT. In the event the CRT is operated at a lower black level, e.g. 0.01 cd/m2, the EOTF will provide a better match with LB set to a lower value such as 0.0 cd/m2. When it is necessary to more precisely match a flat panel display characteristic to a CRT, the alternative EOTF formulation specified below may provide a solution."

SpectraCal graph is for display with 0.05cdm/m2 black, so is this why you have this misalignment compared to pure 2.4 gamma curve? What if you use OLED display which can reproduce pure black. Does then formula change to pure 2.4 gamma curve?

I can't tell if you're joking...?

BT.1886 is the entire equation in that document, which includes γ as 2.40:

L = a(max[(V + b,0])^γ

However, what we call "2.4 gamma" by itself is just: L = (V')^γ

where L = luminance and V' equals the video signal.

The difference is that "2.4 gamma" is kinked as it approaches black, whereas BT.1886 is smooth all the way to black.

Andrew, sorry, did you delete your earlier post? I'm losing track...

I didn't. Still the same.

I thought it's other way around.
Does y=x^2.4 have this soft end?

I'm also bit lost, but what I understand is that they introduced a,b which add correction as TVs are not perfect and for example can't (could not) reproduce pure black.

a: Variable for user gain (legacy “contrast” control)
b: Variable for user black level lift (legacy “brightness” control)

L = a(max[(V + b,0])^γ

so what are a and b for perfect display? a=1 and b=0?

I understand that BT.1886 is not pure 2.4 gamma curve, but equation based on 2.4.

L = a(max[(V + b,0])^γ
so what are a and b for perfect display? a=1 and b=0?

Yes, I suppose so. That would make sense. a and b in BT.1886 account for those legacy contrast and brightness controls.

So then it's L=V^2.4?

Yes, my understanding is that different, newer display technologies have intrinsic black level lift, which is the reason to go with BT.1886 rather than "2.4."

And I have also heard that there are people going with 2.35 gamma. So there's some different interpretations of what BT.1886 is.

SpectraCal/Calman has a good paper on BT.1886 at this link:

http://www.spectracal.com/Documents/Whi ... T.1886.pdf

The EBU standard gamma for rec709 was an accepted 2.35 for a long time. It has now been changed to 2.4. This is about as close as we can get to BT.1886. It is VERY close.

BT.1886 is for the display so it takes into account its capabilities. It seams to be more than simple gamma curve. SpectraCal document shows it and makes some sense.
How it should be interpreted inside processing chain for software like Resolve is another "problem".