Originally Posted by sethk
Thanks for posting this. I'm somewhat confused by the numbers and captions. How does a "Native 14000:1" projector achieve a 14000:1 "intra-image simultaneous" CR with 100% stimulus?
Yes, GlenC has it right. A person cold also think of the extreme intra-image contrast case of an all black screen with a single 100% pixel.
Intra-image contrast is the contrast of darkest spot in the image vs the brightest spot in the same image (not in sequential frames, because that wouldn't be intra-image contrast.)
Are you telling me that a 14000:1 native CR projector could actually measure 14000:1 with total black and total white in the same image?
Yes, theoretically a 14000:1 native CR projector could measure close to 14000:1 within the same image. I say theoretically because it's difficult to measure very small areas of full white. The static contrast measurements here
show this sort of a relationship although we currently only have data down to 0.5% white (by area). Wm has taken measurements as low as 0.1% white (with correspondingly higher contrasts), but it becomes more difficult to fill a probe sensor with that small of an area.
What does this graph really plot?
It shows the theoretical maximum dynamic contrast for a DI vs the same projector without a DI (iris off) vs a native projector with the same on/off contrast as the DI is able to achieve. The maximum dynamic contrast can only happen when the APL of the image is low so that the blacks aren't washed out. So this means a very small area of "white". This small area of white is then varied in brightness from full white (100%) to 0% and the maximum effects of gamma boost for the full range of white stimulus is plotted. This scenario uses measured VW50 data from the static contrast benchmark for iris off and iris 1 modes, but with extrapolated white levels for a 2.5 gamma along with the assumption that the blacks at each step are unchanged from the measured minimum full black. Actual measured results may vary although for illustration purposes it describes the relationships and what one would expect quite well.
In essence the DI (with dynamic gamma) allows a projector to better utilize the limited contrast that it has with a wider range of pixel brightness than what would be the case otherwise (ie w/o the DI). Although this flexibility comes with a price (brightness compression for example).
EDIT: I see Stranger89 and I are thinking along the same lines