Blackmagic Forum

Davinci has different gamma options in Color Management project setting or OFX plugin, which are 2.2, 2.4, 2.6 and then there is just plain Rec709.

The question is, what gamma curve does it have? Is it BT1886?
I work on 2.4 monitor for now, and it looks too contrasty if that option was BT1886.

Thanks in advance.

It can be 1.96, 2.2 or 2.4 or BT.1886 depending what developers decided to put under the name.
In Resolve it looks like it's either 2.4 or BT.1886.

Andrew Kolakowski wrote:It can be 1.96, 2.2 or 2.4 or BT.1886 depending what developers decided to put under the name.

comparing all the gammas makes me think it's not 2.2, 2.4 or 2.6.
It looks wrong for BT1886 either, but I can't check that.

That's why I want to know for sure which gamma it is.

When you set 2.4 and Rec.709 they give same end preview, so I assume they are the same.

I would also like to know what is hidden under Rec.709 name. Gamma for Rec.709 on the display side was never defined (which translates to: whatever display does it's Rec.709 gamma?) until BT.1886 came.

Andrew Kolakowski wrote:When you set 2.4 and Rec.709 they give same end preview, so I assume they are the same.

Doesn't work that way for me. Testing on greyscale ramp and converting it to different gammas gives me different result.

Is this not 1.96 then?

Andrew Kolakowski wrote:Is this not 1.96 then?

may be, we can only guess. Why is that when there is BT1886 standard - I don't know.

BT.1886 is bit more complex as it takes into account display possibilities and have offset values. It's hybrid curve based on 2.4 gamma (but not pure 2.4 curve). This is why many people say that BT.1886 is 2.4 gamma.

This is good explanation:
http://www.spectracal.com/Documents/Whi ... T.1886.pdf

As far as I understand idea is that if you have 2 displays (specially e.g. LCD and OLED) and you calibrate them with BT.1886 then they should look closer to each other than when you would calibrate with pure eg. 2.4 gamma. Those 2 offset parameters allow to compensate for display technology differences (like OLED and LCD). This is how I understand it.
Also- does it mean that in every TV which has BT.1886 choice actual curve is different (based on particular TV capabilities?


This is also quite interesting and good summary (from lift gamma gain forum):

Code: Select all

hm..yes..interesting question. 2.22 would be close but better would be a correct conversion from your "personal" BT1886 curve, not sure if that can be done with any software?

"The full BT.1886 specification is complex and its precise recommendations vary depending upon the white level, and especially the black level, of the display. However, if you don't want to bother with a precise BT.1886 calculation, white/black values of 120/0.03 cd/m2 serve as a good rule of thumb. This results in a gamma response between 2.3-2.4 at the top end and 2.2-2.1 on the low end." - from http://www.chromapure.com/colorscience-gamma.asp

"2.3-2.4 at the top end and 2.2-2.1 on the low end." = close to 2.22, there is a post from Steve Shaw.