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Old 09-29-2013, 07:11 PM
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old_tv_nut old_tv_nut is offline
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Quote:
Originally Posted by Username1 View Post
Inx64;

Your color "gamut ICE " graph is wrong, in the green by a lot..... Someone here did those measurements and posted them on one of those 15gp's and another tube, and while people maintain the 15g's had better "full"gamut, the graph they posted showed a smaller triangle, than the other tube. I would sure be interested in seeing the response of your tube again, once you figure out what is going on with the green.... Also, try it and be sure that when the screens are turned down, the tube goes into cutoff. I have no idea how the test is run, but I find this testing interesting...
??
Not sure I follow what you said.

Inx64 did not explain his colorimeter software, but I believe what the CIE gamut display is showing is:
The light colored triangle and square boxes are the aim points for REC709 (HDTV) or sRGB monitors. The circles are the measured points for his set.


edit: bottom line, his green is not wrong, but is fairly typical for all tubes with sulfide green, which is all tubes after the 15GP22 and 21AXP22 (don't recall what green was in the 21CYP22 at the moment).


You can see that the triangle made by the RGB points for his set is slightly smaller than the REC709 spec because the green is slightly yellower.

The magenta is far off from the aim point towards red, and this has to be because of the demodulator gains and angles in his set, since moving the green primary towards yellow causes the magenta to move towards blue in order to keep the white point within spec (which it is). This error in magenta is not necessarily a bad thing, since it helps to prevent purple faces when there is an error in burst phase, and there are few recognizable magenta/purple objects (except maybe Barney the dinosaur). 2nd edit: it also compensates for the movement towards blue of magenta caused by the yellowish sulfide green, making the magenta a closer approximation to NTSC magenta.

A 15GP22 or 21AXP22 CRT has a green that is much less yellow, so the triangle is larger on the cyan side; but the blue in those CRTs is less violet and more cyan, so the triangle is smaller in the blue/purple area.

Last edited by old_tv_nut; 09-29-2013 at 07:22 PM.
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