Tweaking CRT to correct color/plunge at

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Old May 6th, 2007, 02:41 PM   #1
Regular Crew
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Location: Sarasota,FL.
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Tweaking CRT to correct color/plunge

What is the best way to calibrate my CRT/tv to have the correct color
and brightness for use as a video monitor ?? I just read an artical about
using a Wratten 47 B dark blue filter,and using my cannon GL-2 on board
SMPTE (NTSC) color bars to set chroma/hue etc.
is this the approach I need ,to pursue??
Perhaps there is easier way.

As always, your input is appreciated.

Blayde @ Cornerstone
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Old May 6th, 2007, 03:02 PM   #2
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You're headed the right direction but you shouldn't use the colour bars from your camera to do the calibration. Most editing software has the ability to output reference bars and those are what you should use. If yours doesn't have them, you can get a DVD such as the Avia DVD for home theatre setup and use those.
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Old May 6th, 2007, 05:23 PM   #3
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1- The blue gel trick doesn't work perfectly since the green phosphors emit 'blue' wavelengths that get through the filter. One trick to do is to use alternating color bars... you take your color bars and superimpose flashing squares of the opposite color onto it. The Avia calibration DVD shows this, as do the VASST titles on color correction in Vegas or FCP (vol.4 for vegas, vol. 8 for FCP).

2- Some consumer CRTs can't be calibrated to color bars. They decode colors/red incorrectly to make reds (and flesh tone) look right.

3- The Avia calibration DVD may not work well since your DVD player may output different levels than your cameras.

A lot of DV cameras put black level at 0 IRE instead of 7.5 IRE. (This is a cost-saving measure I believe.)

DVD players in the North American market tend to put black level at 7.5 IRE instead of 0 IRE.
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Old May 6th, 2007, 08:28 PM   #4
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Most video equipment is made from Japan design where NTSC black is 0 IRE not 7.5, hence all the DV cameras( they are mostly designed in Japan) will output 0 IRE not 7.5 from their analogue outputs. DVD players destined for North America are normally designed to correct their analogue output to 7.5 setup but in Japan will be 0. Consequently of course the TV's are different, one expecting 0 the other expecting 7.5 all to account for the inadequacy of electronics of many years ago in North America. So feed your North American TV an analogue signal from your camera and it will be darker than you expect and darker than if you make a DVD from it and play back to the same TV!!!!!! IF you output to a really old TV it may well not hold vertical sync ( picture will roll ) the reason for the 7.5 IRE guardband to separate the sync from video. There are lots of topics on this if you do a search.
Thank goodness that with digital inputs to new TV's this will all go away and finally North America will catch up to the rest of the world.

Ron Evans
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