Comment by Animats | Hacker News Reader

Comment by Animats | Hacker News Reader

From the article: "As the electron guns sweep across the screen, varying their intensity to adjust brightness, they tend to overshoot their desired value and bounce back a short time later. This creates alternating vertical bands of light and dark seen at the edges of high contrast changes in brightness."

That's caused by a different effect. NTSC has terrible color bandwidth. The YIQ signal is really an I (intensity) signal at full bandwidth, and YQ signals with severely limited bandwidth (because, during the transition from black and white to color, they had to be stuck in subcarriers of the main black and white signal. NTSC Color TV is really greyscale TV with color tweaks superimposed.

You can only go through the YQ color space about 10 times across the width of the screen. The way to simulate this is to convert to YIQ, apply a low-pass filter horizontally to the Y and Q components, then convert back. Note that this is a horizontal issue only; in the vertical direction, every line can be a different color without problems.

fyi(q), I doesn't stand for intensity, but for in-phase https://en.wikipedia.org/wiki/In-phase_and_quadrature_compon...

Right, NTSC has luminance (Y), I and Q define a vector in the color space, and have much less bandwidth than the luminance signal.

>NTSC Color is really greyscale TV

My old CRT only supported PAL. So this is the reason why NTSC inputs were displayed without color.

Your old CRT is probably PAL-M, a variant of PAL. Was it made in Brazil? https://en.wikipedia.org/wiki/PAL-M#Compatibility

I (scandinavian) have a few old TVs and monitors that are able to synchronize to the NTSC clock, but are unable to decode NTSC colors. It's not uncommon, and even my 1084S does it. As far as I understand this, PAL is just a color encoding standard, and the synchronization characteristics typically associated with it are broadcast standards, e.g. PAL-M, PAL-B etc. If you have a TV that decodes PAL at 50Hz there is a good chance that it will decode PAL at 60 Hz even outside countries that had these broadcast standards.

For NTSC, since it's only really the timing and color encoding that differs it's then not uncommon to get a grayscale picture from NTSC input.

Both PAL and color NTSC are derived from greyscale television standards and represent luminance a similar way. PAL uses a slightly different encoding scheme for color information that improves on some of the deficiencies of NTSC and uses a different color carrier frequency. Since the carriers are far enough apart your PAL TV doesn't even "see" the NTSC color signal and so you just get greyscale rather than incorrectly decoded color.

Back in the day, the joke was that NTSC stood for "Never Twice the Same Color".

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