Originally Posted by rickardl
For a plasma, what pattern would be used for that? window? if so, what size? or maybe ANSI contrast pattern?
So it is clearly a relation between the ambient light in the room and the needed/wanted fL for 100% white on the display.
Given that, shouldn't it be possible to measure the ambient light and then calculate the right amount of light output needed from the display?
Edit: I found a discussion about it here: http://www.avsforum.com/t/1343528/is-this-a-cheap-alternative-to-the-ideal-lume/30#post_20674786
I still use window patterns where the window is about 10% of the area of the screen and surrounded by black. There's a lot of recent hysteria about avoiding all effects of automatic brightness limiting by using either very small window patterns (which are problematic for some meters to read accurately (depends on meter design) and constant Average Picture Level (APL) that maintain the same light output for all windowed patterns. IMO, the plasma TV will never operate without brightness limiting so the calibration should include SOME brightness limiting to help keep images accurate. You can always re-measure gamma with APL patterns to see if it is horrible or not.... if it is not horrible after using "tradiaional" 10%-size windows, you're good to go.
Some software supports subtracting ambient light from meter readings, but ambient light... daylight especially, changes constantly as the sun moves across the sky, as clouds come and go, as leaves on nearby trees appear, change size, change color, and fall again, as sun reflects from nearby buildings at different times of day, etc. If it is only artificial light you are worried about, there's more of a chance of a software's ambient light cancellation working but you'd have to test it to see how it works with your specific meter since meters all work differently and all respond to ambient light differently - mostly influenced by the angle of view of the meter, how close the meter is to the flat panel (obviously, for a projector calibration, ambient light has to be off completely), and how the meter "sits" against the panel.