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Feedback VJ - too much color
MUFF WIGGLER Forum Index -> Video Synthesis  
Author Feedback VJ - too much color
FetidEye
Hi

I am part on an (all analog) videofeedback VJ collective ("de oplichters")

In my setup I use a lot of video equalizers (such as the Videonics EQ-1 and GSE VEP) .

When this "boosted" signal is projected it sometimes looses much color,
while on the TV monitors it is still present. Maybe the beamer is overloaded?

Is there a way to prevent this? (and what is happening?)
snufkin
some things I do to combat this

try to ajust the settings on the projector

use a video corrector to darken the image
daverj
If you have access to an oscilloscope, take a look at the video signal. If the burst part of the sync is too big, or if subcarrier goes too far below the black level then the digital circuits in the projector will turn down the color levels.
lizlarsen
While probably not connected to the specific issue you're mentioning (Dave and snufkin's advice sounds good), it's also worth noting that a color CRT monitor can often display more vibrant and brilliant color saturation ranges than a digital projector.
felixer
yep, same thing here. the pic from the beamer is slightly 'flatter' then from the tv. i adjusted the beamer for a bit more brightness and colour ....
but maybe the tv gives 'too much'? unless it's an expensive/calibrated broadcast monitor i wouldn't trust it's performance too much. i have several old crt's and they all give a different image. no way for me to check which one is accurate ....
daverj
That's one of the uses for a good set of color bars, on tape or live. To adjust all the monitors and projectors in a show (or studio) to look roughly the same.
FetidEye
i agree that crt monitors are the best (that's why we have a lot of those.
downpoit on that is : they're really heavy (the big ones)

and beamers are can project on weird surfaces..

probably daverj is right.

is there something like a video limiter?
lizlarsen
Quote:
is there something like a video limiter?

Sure, that's generally a feature of some proc-amps and broadcast gear (clipping the white level and limiting the chroma gain.) That doesn't really address the issue at hand though. My guess is that the projector in question just won't give the same kind of color saturation range as a CRT monitor will.

My Color Video Encoder module precisely clips voltages outside of valid levels that would cause any sort of projector glitching. I think Dave's upcoming Output Amp does something similar as well. That's why these are "any voltage in, always valid/stable video out" types of devices.

If you're talking about a "compressor" type (soft limiting) feature, that is -- stretching the overall brightness range closer to white, this can be achieved by gamma correction (exponential or logarithmic amplification.) A triple voltage-controlled gamma processor is something I'd like to release as a module at some point.
barto
perhaps using a projector with a higher lumen rating would look better? seriously, i just don't get it
FetidEye
yeah but we make do with "surplus" materials... not rich enough smile
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