Originally Posted by HDTVChallenged
Kind of a Calibration for Beginners' question.
Yes. Perhaps I should have read around here
more before posting. If I had, I would have found this interesting discussion:
99.9% of the time (gamma) calibrations target the basic power law function (or a slight variation thereof.)
Recently (within the past 1.5 yrs,) there has been some (glacially paced) movement toward BT1886 on displays that are capable of approximating it without any nasty side-effects ...
That is helpful, thank you. I do wonder about this basic power law function. Here's a plot of a power function:
The blue points represent calibration points for a TV with a poor MLL. What I mean by that is that they represent a certain TV's response at stimulus levels of 0%, 10% and 20% after calibration.
The first point could be moved upward by adjusting the TV's brightness control, but it can't be moved down below the MLL. The second and third points could be moved by, say, using 10-pt gamma controls. Clearly there is a problem in that the dashed section of the gamma curve cannot be accurately targetted with this TV. I would imagine this is a well-known problem.
The other thing that is bothering me is this: most TVs have quite coarse-grained calibration controls. So the gamma response might be adjusted at, say, 10 points. But that only matches those particular
points to the target curve. How do TVs deal with all the intermediate points? Do they reproduce what is essentially a piecewise linear function? I.e., something like the green curve below?
I have to emphasize that the graph is for a TV with an exceedingly poor MLL. Which is in fact the MLL (0.24 cd/m^2) that David Katzmaier measured on the DT50, so it's perhaps not impossible to find an example that is that awful. For a better TV, such as one of the recent Panasonic plasmas, a much closer match to the target curve would be possible.
My apologies for being a complete beginner and any abuse of terminology that might cause :--)
Thank you for your patience.
[EDIT] Perhaps I should say in passing that my labelling of the power function is somewhat misleading. What I've actually plotted is a graph of 100(x/100)^2.4. 100 cd/m^2 is the target peak luminance.