Originally Posted by jasperm
I'm having some difficulty understanding the difference between correcting color push vs setting color temp/white balance. I understand (I think) that red push means increasing the "drive" to the red gun and we want to get rid of that to get more even color balance - but doesn't this also interact with the color temp settings? Drive and Cut?
These concepts are easy to confuse. No, red "push" is not related to white balance at all. (You likely already understand the first part of the explanation, but I'll state it anyway for others' benefit.)
Setting a perfect white balance and grayscale can be accomplished in the *absence* of any color at all. Just as with TVs of 20-40 years ago, the xCUT controls determine when the screen starts to glow as the video-signal voltage increases from its minimum, on its way from black to white. Ideally, all of the color guns start to glow at the same time, and you get neutral dark gray. But this isn't how CRTs generally behave, and it is tuned by using different settings of R-, G-, and BCUT.
As the video signal reaches the value for "white," ideally all three color guns contribute the right amounts to produce a pure white, which is defined in the video-production world as 6500K -- roughly the color of front-lighted white clouds at mid-day. Whereas the xCUT controls determine at what point the color guns *begin* illuminating the screen, the xDRV controls determine how much "drive" each gun gets as the video goes from "black" to white. You would adjust R-, G-, and BDRV to get that perfect white, using a known white pattern or a high-contrast TV picture with color turned all the way down.
The xCUT and xDRV adjustments interact. (To an engineer they are classic offset-and-gain adjustments.) A 5-point change in RCUT makes a big change in color of dark gray, but very little change in the color of white because those 5 points are now only a small percentage of the total white. Likewise, the xDRV controls slightly affect the color of dark gray. Obviously one goes back and forth between the two control groups until everything looks fine. And generally, if you get the darkest grays and white right, the grays in the middle are fine, too.
Now that you have a perfectly-calibrated grayscale and white point, we introduce color. But here's where "push" comes in: It is the *favoring* of certain colors by the process that extracts the color from the TV signal, whatever it is. Imagine a picture of three kids with red, blue, and green tee-shirts of equal intensity in the real world, standing on a gray concrete driveway. Some TVs will show the red shirt as much more intense than the others, as with all other reds in the picture. (White and grays, by the way, and that driveway are still perfectly neutral.) This is "red push" -- a *favoring* of red in the color-decoding process. Whatever the historical arguments for this regarding NTSC broadcast deficiencies, color push is now considered a no-no, and *accurate* color decoding is preferred. (Matches reality, no?)
Sony's late-model computer-driven TVs have exquisite controls for all of this in their service-mode codes: Grayscale and white can be finely tuned (basic controls: xCUT and xDRV), and color-push can be reduced to virtually zero with 2170P-4/RYR thru GYB plus a good test pattern from, say, the DVE DVD. Plus, the TV will store two different sets of values for RYR-GYB, for the "Default" and "Monitor" user-menu choices.
Are these two calibrations affecting totally independent aspects of how the image is produced?
Different aspects of how the video is processed by the TV and then displayed, yes.
Or alternatively, if I change the color temp via the approach outlined early in the thread, wouldn't that alter "push"? Or more importantly, wouldn't correcting push alter color temp?
Nope, they're independent.
. . . working for Eastman Kodak, where I did a bit of work on circuits related to control of CRTs in photofinishing equipment. So theoretically, I ought to understand this very well.
If you think of TV color-push as analogous to a specific color film's "personality," you may come close. When you worked with color CRTs for photofinishing, color push would have been an unacceptable defect, I would think, as it is with the color-prepress monitors I have set up. The "push" is created by the TV for an "esthetic" purpose.
Unfortunately, TV manufacturers keep throwing these color "improvements" at us, and we have to keep getting rid of them. Lucky it is that, with these Sony sets, it's a relative breeze. With some older sets, there is no way to alter the color decoding.
My experience, and that of several other posters here, has been that the following settings generally kill all color push for the XBR960 and recent XS955 CRT TVs:
2170P-4 / RYR-RYB-GYR-GYB = 13-15-5-3. (Then WRITE the settings.)
But grayscale and color depend heavily on your particular CRT and its characteristics.