Greetings

As a newbie, I'm trying to learn the measurement icons of colourspace, but there are some things I don't understand, and I think I want to understand the charts better, and more importantly, the underlying algorithms

Attached below is the grayscale data that I measured offhand and compared to SRGB gamma (it seems like full luminance is a power function of 2.2), but when I was looking at the absolute error of dif eotf, I know it is correlated to luminance but don't understand why it is the Y value that is 0.7218, and I am trying to compute gamma=log( 0.1495)/log(0.5294)=2.988091273 and the SRGB gamma=log(0.2468)/log(0.5294)=2.199925804 for the comparison, I thought it was 2.988091273-2.199925804=0.788165468 but it doesn't correlate with it being the Y= 0.7218 is the same

So, I'm curious how this value Y=0.7218 is calculated? Why is it above the 0 axis?

Thanks a lot!

Because you have a target of 200 nits peak, and a displays that can only make 123 nits.

Steve

Steve
Thanks for the reply!

Yes, the target brightness of 200nit is my own deliberate modification to clearly distinguish my measured eotf from SRGB's eotf and make it easier to observe the relationship and trend of the charts

EOTF I understand the meaning of the two curves, because by putting two EOTFs with different maximum brightnesses in one chart, my measured maximum can only be lower than the SRGB's maximum Y=122.985/200=0.614925

But in the ABSOLUTE ERROR dif eotf chart, they are also presented in one chart, and need to reflect the effect of luminance as well, and the axis of Y=0 means that SRGB's gamma=2.2, right? So, my measurement Y=0.7218, how is that calculated?

Does it mean that my measurements have gamma=2.2+0.7218=2.9218?
For comparison purposes, do they perform any luminance mapping?

haha, don't know much about it, please enlighten me!
Thank you very much!

All I am going to day is that obviously the values of Black and While alter the target luma values for any given point in the EOTF.

Steve