Color Phase at DVinfo.net

Lizi Hesling · August 29th, 2007, 12:36 AM

I know this is a silly question, but I can't find an answer anywhere - please could someone explain to me what color phase is. I've been fiddling with it under custom presets - I can see that it seems to change the red-green balance, but in what way is it different from red gain and green gain?

Thanks

Greg Boston · August 29th, 2007, 12:58 AM

Color phase is like the tint control on a tv set, whereas color gain would adjust the saturation. If color gain is set to minimum for all three colors, you get a black and white picture.

So here's the history lesson part...

The color phase was developed by the NTSC as they instituted color television many years ago. To transmit color, there is a 'chroma burst' signal (a subcarrier at 3.58 mhz to the main channel frequency). The instantaneous phase difference between that signal and the reference in the tv set that gets synchronized at the beginning of each scan line, determines the actual color while the amplitude of that signal represents how saturated the color is (ie: light pink or bright red). There are separate signals for red and blue but not green. The reason being that green is the predominant color in most scenes and by saying R+G+B=100 percent of the color, you can figure out the percentage of green by knowing what percentage the other two signals are. This saves a lot of bandwidth in transmission.

End of history lesson.

So by adjusting color phase on your camera, you essentially alter a reference that makes colors show up at a different degree than where they are expected and the visual effect is a change in tint. This is represented by the 'vector scope'. It shows color phase and amplitude.

-gb-

August 29th, 2007, 12:36 AM	#1
Lizi Hesling Regular Crew Join Date: Mar 2003 Location: Beijing, China Posts: 40	Color Phase I know this is a silly question, but I can't find an answer anywhere - please could someone explain to me what color phase is. I've been fiddling with it under custom presets - I can see that it seems to change the red-green balance, but in what way is it different from red gain and green gain? Thanks

August 29th, 2007, 12:58 AM	#2
Greg Boston Wrangler Join Date: Oct 2003 Location: DFW area, TX Posts: 6,117 Images: 1	Color phase is like the tint control on a tv set, whereas color gain would adjust the saturation. If color gain is set to minimum for all three colors, you get a black and white picture. So here's the history lesson part... The color phase was developed by the NTSC as they instituted color television many years ago. To transmit color, there is a 'chroma burst' signal (a subcarrier at 3.58 mhz to the main channel frequency). The instantaneous phase difference between that signal and the reference in the tv set that gets synchronized at the beginning of each scan line, determines the actual color while the amplitude of that signal represents how saturated the color is (ie: light pink or bright red). There are separate signals for red and blue but not green. The reason being that green is the predominant color in most scenes and by saying R+G+B=100 percent of the color, you can figure out the percentage of green by knowing what percentage the other two signals are. This saves a lot of bandwidth in transmission. End of history lesson. So by adjusting color phase on your camera, you essentially alter a reference that makes colors show up at a different degree than where they are expected and the visual effect is a change in tint. This is represented by the 'vector scope'. It shows color phase and amplitude. -gb-