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  • Joined: 20 Sep 2021
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master system colors
Post Posted: Mon Sep 20, 2021 12:53 am
Hello everyone, just time posting but I've been a big fan of these forums for quite some time. I hope someone has an idea about a slightly annoying issue I have with my NA master system.

The colors are pretty close, but in text, thinner parts of letters have a pink or purple hint to them. I'll attach photos as an example of how it should look, vs how mine looks.

I originally just had composite cables of differing qualities and just also tried SCART (which is so awesome and did a great job cleaning up the picture) but this issue remains.
Thanks in advance!
right.png (835 KB)
right.png
wrong.png (1.29 MB)
wrong.png

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  • Joined: 05 Dec 2019
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  • Location: USA
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Post Posted: Mon Sep 20, 2021 1:43 am
Color fringing is a common trait on Atari and Sega consoles.

Composite video encodes brightness (or "luma") and color (or "chroma") information on a single wire pair by converting the chroma into a pattern of light and dark dots superimposed over the luma. The TV decodes the dots by comparing their position to the colorburst, a reference signal to the left of the visible area of each scanline. If a stroke is too narrow, it may be interpreted as a color dot instead of pure luma. This misinterpretation is called "color fringing," and it can be analyzed as crosstalk between the chroma and luma signals.

A standard TV signal arranges the colorbursts such that the chroma dots form a diagonal pattern. So do company N's consoles. That makes fringing harder to see, except in checkerboard dithering or the diagonal stripes of a talking head's necktie. Atari and Sega consoles, by contrast, line up the chroma dots vertically. This produces color fringes on thin vertical strokes. Rainbow fringing becomes even easier to see in Mega Drive that use tight vertical stripes in H40 mode, as those are at a frequency very close to that of chroma dots.

SCART can carry both red-green-blue (RGB) signals and composite video. If you still see color fringing over SCART, one of a small number of things is probably happening:

A. The console isn't generating RGB, and the TV is falling back to the composite signal.
B. The TV doesn't support RGB input and is paying attention only to the composite signal.
C. You bought a substandard SCART cable that only carries composite.
D. The console internally generates composite, decodes that to RGB, and sends that over the SCART RGB lines. Hasn't been seen on SMS or MD, but it's known to be done in one of company N's consoles sold in France.
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Post Posted: Mon Sep 20, 2021 3:11 pm
Thanks for much for the info. I'm happy to know of the term "color fringing" to help with research too, I couldn't find a term for it.
I'll try a different SCART cable, the one I got was one of the "cheapies" from Amazon. It still did a great job cleaning up the picture as far as static and visible noise goes, but I'll hunt for one of the high quality SCART cables and see if that helps. I'll report back with my results
Thanks again!
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Post Posted: Mon Sep 20, 2021 4:24 pm
Cheap SCART stuff is sometimes composite only. The composite signal is generally needed to give the synchronisation data for the RGB signal.
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Post Posted: Mon Sep 20, 2021 8:49 pm
I'm searching for an alternative master system SCART cable, they seem tough to find. The one I bought did specify that it was RGB, but I'm certainly willing to rule it out.
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Post Posted: Mon Sep 20, 2021 10:28 pm
ericthehammer wrote
I'm searching for an alternative master system SCART cable, they seem tough to find. The one I bought did specify that it was RGB, but I'm certainly willing to rule it out.


Does your tv support rgb over scart as well?
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Post Posted: Mon Sep 20, 2021 10:28 pm
If possible, check your TV’s menus or settings. It may be possible to make it show the mode (RGB vs composite) or to select which one is used when both are present.

Another factor I seem to remember is that some TVs with multiple SCART ports would only support RGB on one of them.
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Post Posted: Mon Sep 20, 2021 11:57 pm
Maxim wrote
If possible, check your TV’s menus or settings. It may be possible to make it show the mode (RGB vs composite) or to select which one is used when both are present.

Another factor I seem to remember is that some TVs with multiple SCART ports would only support RGB on one of them.

Wow I feel a bit embarrassed. Apparently after selecting SCART, there was in fact a second option for composite or RGB. Sometimes I'm not so bright lol.
It's amazing how different SCART is. I'm just starting to learn of it.
Thanks so much! It has solved this issue.
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Post Posted: Tue Sep 21, 2021 2:42 pm
PinoBatch wrote

A standard TV signal arranges the colorbursts such that the chroma dots form a diagonal pattern. So do company N's consoles. That makes fringing harder to see, except in checkerboard dithering or the diagonal stripes of a talking head's necktie.


Is that why vertical lines on the NES often look jagged?
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