Hi Pete,
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Originally Posted by Pete Deksnis
Not sure what the exercise will demonstrate.
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This file has 100% saturated colors and 100% white. The reference color bars usually have 75% saturated colors due to the fact that the amplidute of the red signal might be overloaded with 100% saturated color. So, with this file you can test whether the RGB drive is proper operating. (If the tubes are tested good on your CT-100, it should operate properly.)
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Take a 'perfect' or reference color bar (as you have provided) and reproduce it on an sRGB TV or monitor driven via component or DVI or HDMI, and you get a 'perfect' (okay, really, really good) color bar image. I've done that and photographed the sRGB-phosphors screen with an sRGB digital camera and generated an sRGB color space jpg. It can be seen here.
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For comparison: I have displayed the color bars on my computer monitor, and photographed it. See the file in the attachment. You can see that there is a bias toward blue in the green, but the other colors seems to be OK (within a large range of standard error). Now you can compare the monitor screenshot with the screenshot of the 21AXP22A.
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That same reference color bar signal turned into an NTSC signal by a DVD player [and either modulated or directly introduced into the first video amplifier (which is the way I do it)] is going to be corrupted or at least constrained by the NTSC system and the DVD-player version of NTSC. I think I would see what I see now since the color bar pattern on my DVD is essentially reference quality before it takes the long NTSC route to my 15GP22 screen, and as I have noted above, the brightness/contrast range is already adjusted correctly as shown on a screen shot earlier.
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I feed the video signal as R.F. signal directly into the tuner of the CTC5. So I get a nearly perfect impression about the disadjustments and the losses in the color channel up to the screen of the 21AXP22A. (Note that I have to convert the PAL signal into NTSC which means an additional loss of signal quality, especially in the transit between magenta and green.)
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There is another factor not yet mentioned -- that of high-voltage. Your CTC5 has what, 25 kV to play with and the regulator is far better than the 6BD4 circuit used in the CT-100.
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High voltage in the CTC5 is 19.5 kV according to the manual, and I have controlled it.
I believe that your CT-100 has a much better color performance than it is shown here in your demonstrations, and this is what I want to prove with these tests. When I got the CTC5, I misadjusted color and brightness a lot of times before I understood how it works. I did only know the PAL tv sets, and they are working different.
- Eckhard