As I have posted in other threads, I am currently playing with the gamma tables on my Davis projector.
One thing I noticed is that it starts outputting light at just 1% IRE. If I watch a movie with a black background, that's at 7.5% IRE, and the blanked background from yxy is 0% IRE, and it's clear that they're different.
So, my plan was to compress the gamma ramp, by moving the 1% IRE point to 7.5% IRE. I would compress the light output values up until (I picked out of a hat) 20% IRE. So, if the output value went from 1 at 1% IRE to (say) 500 at 20% IRE, I changed it to go from 1 at 7.5% IRE to 500 at 20% IRE. So, in the 7.5 - 20 IRE range, it will start blacker (actually black), but have a steeper slope.
Anyway, I tried this, and watched the Matrix, and the dark scene in the beginning, I could see tons of video noise! I guess I was seeing lots of shadow detail - in fact more than what was actually there in the data signal!
Does anyone have any comments? Instead of doing the modification up to 20% IRE, I could do it over a wider range, say to 50% IRE, or even up to 100% IRE, and then the slope difference would be much less.
I *do* want my projector outputting nothing at 7.5% IRE, right? (I'm assuming my DVD is not in any kind of 0% IRE mode where it remaps 7.5% IRE to 0% IRE.)
Mike
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Join the NYC-area HT club! Send me e-mail!
One thing I noticed is that it starts outputting light at just 1% IRE. If I watch a movie with a black background, that's at 7.5% IRE, and the blanked background from yxy is 0% IRE, and it's clear that they're different.
So, my plan was to compress the gamma ramp, by moving the 1% IRE point to 7.5% IRE. I would compress the light output values up until (I picked out of a hat) 20% IRE. So, if the output value went from 1 at 1% IRE to (say) 500 at 20% IRE, I changed it to go from 1 at 7.5% IRE to 500 at 20% IRE. So, in the 7.5 - 20 IRE range, it will start blacker (actually black), but have a steeper slope.
Anyway, I tried this, and watched the Matrix, and the dark scene in the beginning, I could see tons of video noise! I guess I was seeing lots of shadow detail - in fact more than what was actually there in the data signal!
Does anyone have any comments? Instead of doing the modification up to 20% IRE, I could do it over a wider range, say to 50% IRE, or even up to 100% IRE, and then the slope difference would be much less.
I *do* want my projector outputting nothing at 7.5% IRE, right? (I'm assuming my DVD is not in any kind of 0% IRE mode where it remaps 7.5% IRE to 0% IRE.)
Mike
------------------
Join the NYC-area HT club! Send me e-mail!
