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| Re: Remember TV Test Patterns? (252482) | |||
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Re: Remember TV Test Patterns? |
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Posted by SelkirkTMO on Wed Oct 10 03:37:13 2007, in response to Re: Remember TV Test Patterns?, posted by tracksionmotor on Wed Oct 10 00:13:22 2007. Ah, the wonderful world of DC propulski ... as obsolete as variable capacitors in a varactor world. :)Vectorscopes are used to set the burst level, phase and amplitude of chroma ... the burst is the little tick there at 270 degrees, and the objective is to align the amplitude and phase of the chroma signal so as to hit the smallest boxes perfectly from a "split field color bar signal" as follows:  A split-field color bar signal looks like this and produces the above:  An improved color bar set to the "EIA with pluge" as shown above is called "SMPTE Color bars" which adds a nicely generated additional set of reverse bars in a slice which looks like this:  A vectorscope will present them similarly, but because of the reversed colors in the stripe, will show amplitude distortion as well which causes the vectorscope to display curvy transitions as opposed to the straighter transitions and indicates nonlinearity in the video amplifier. And SMPTE bars offer a tremendous advantage in field production if you have a monitor which has a "blue-only" switch which shuts off the red and green guns on the CRT. You can adjust WITHOUT a vectorscope on one of these bad boys visually. Crank up the color so that the two outer bars match all the way from bottom to top through the slice, then adjust phase so that the two inner bars match as well ... PROPER monitor setup by eyeball! :) This example is set with proper phase, but slightly reduced chroma level, to mismatch the top and the slice so that you can see how it works:  Taa-daa! :) |
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