Quote:
Originally posted by MrWigggles:
Mark,
I haven't seen them yet. I am only guessing that they help the projector's gamma. Going from the 2.5-ish gamma under the pre-programmed 'normal' settings to a 2.2 type gamma flashed into a natural 1 or 2.
A while back I sent him a Matlab program that can hopefully further improve his results.
Gary, keep us informed.
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Sorry for the very long delay in getting back. I have been looking at a couple of different gamma curves on my post Thumper LT100 for the past 3-4 weeks. Wigggles sent me a matlab file to try out a couple of curves and I had a few ideas I wanted to try.
It is a long story and getting late so I will make it brief and try to elaborate more tomorrow. I was wondering what general gamma correction that we want, and originally tried an inverse of Gamma 2.2. The picture was very nice but I felt that the detail in the low light areas (near black) could use some work. It seemed like any below say 10 IRE looked the same. I found out that the source material is not recorded with a straight gamma of 2.2 but has a straight section near zero and in general climbs out slower (this is the encoding using the Rec. 709 equations used by HDTV). I assume this is similar to what is used for DVD recording.
Please see:
http://members.home.net/g.p.gibbs/
Next I tried implementing the inverse of the Rec. 709 that was applied to the source. ASSUMING the DLP is ideal and has a linear input/output (big assumption but all I can go on given my lack of test equipment, etc.) then if we inverse this Rec 709 equation we will reproduce the original source. Results definitely showed that the black detail could be drastically increased, but at the expense of seeing all the noise in the black.
Then I decided to look for a compromise. I want more detail in the black and a little more punch in the midrange compared to gamma 2.2, but I did not want to go as far as Rec 709.
In the curves shown on the referenced page you can get an idea of what the gamma curves for straight gamma 2.2 vs. rec 709 vs. Wigggles suggestion vs. my guess at what would look good. You can see that Wigggles and my curves are very similar at the low end. They are brighter then the gamma 2.2 but not as bright as the Rec. 709. I think this is a good compromise. In the mid to high end think that Wigggles curves are a little hot and remind me of the hot whites days
http://www.avsforum.com/ubb/eek.gif http://www.avsforum.com/ubb/smile.gif
In summary I have been looking at all four of the curves (and also straight gamma 2.5) for several months and the last month I have been switching between Wigggles and my hybrid. I have been most happy with my hybrid and would consider it a nice improvement over the "normal" gamma available from the factory. This is assuming you have had Thumper work the magic. I was playing with this before the Thumper mod and feel that the Thumper mod is a must. The gamma correction does make a nice improvement in the low end (where it could be used), but is not as dramatic of an improvement as the Thumper mod.
This ended up being longer than I expected. Excuse me if I have said anything wacky. It is getting late here.
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Gary
STOP DVI/HDCP!
DVI/HDCP! ~= HD-DIVX!!!
DO NOT SUPPORT JVC or anyone else who supports this!
