NTSC Composite Color Palette

RetroArch Additions Shaders
#1

Hi.

This is my first post.

I was looking to some screenshots comparing NTSC Composite and RGB and I was shocked how different the colors looked between them. I’m not talking about color artifacting or blurriness at all, I’m referring to luma and chroma aspect of color. First, take a look at the screenshots (Warning: The pictures require hovering your pointer over the images to make them work!): Sega Mega Drive NTSC composite vs. RGB Other Systems NTSC composite vs. RGB

So if we had RGB to have NTSC composite colors without artifacts, it would look something like this (simulated) picture: Compare it to the raw RGB screenshot: For referrence, here is the real NTSC composite screenshot: What we are getting in the first screenshot is a razor sharp and perfectly clean picture with the more “authentic” colors some of us are more used to see from back in the day.

With that out of the way, questions: Was it done already?. Did somebody else looked into this?.

I’ve been trying with some existing shaders like color mangler, I tried to convert picture to YIQ/YUV and mess with the channels, I tried to create a LUT table on Gimp and apply it using LUT.glsl, but nothing worked. If I got some picture to look good, I was bound to find a lot that didn’t. In fact, most colors got out of whack!. Maybe if I had something more useful and standard, like a screenshot of the RGB scale from 240p suite?.

Well, guys, what do you think?

#2

Have you tried taking one of the default passthrough LUTs into Photoshop and using filter > video > NTSC Colors (https://forums.adobe.com/thread/1289449)?

Other than that, there are some things you can do for NES, specifically the NTSC color palettes and the raw palette decoding shaders, but these strategies can’t work with other cores.

GTU also has an option to enable composite colors, and the new “artifact colors” shader does a good job of it, too.

#3

Hi!, thanks for replying.

I don’t have Photoshop now, I have Gimp and I tried converting to Y’IQ and Y’UV, but picture had no perceptible change.

I’ve been looking at the shaders you suggested, but they seem to be artifacts oriented.

I tried “ntsc-colors.glsl” shader, but it’s not for this.

I cannot match colors to the reference screenshots I pointed at. It’s very tough to make reds lean toward orange without making yellows reddish in the process. Or making green darker, without messing with yellow, just to name a few hurdles. There has to be some algorithm or something, but I leave that to you or the other experts.

#4

I don’t think there’s going to be any sort of color transform that’s going to look right in part because the NTSC colors are influenced by the surrounding pixels. That is, it’s more than just switching to a different colorspace. Once in YIQ, there’s a bunch of stuff that needs to happen to the signal, including running through a low-pass filter and a comb filter, modulation and demodulation, before converting back to RGB and that stuff is where the color changes come from.

#5

But that just makes me wonder, if that’s the case, why do current shaders differ so much from the images posted on that site in color? I mean, maybe the context and the things you mentioned have the greatest weight in the final colors, but there is some change of tone missing, those reds orange and yellow browns, yellows very bright, greens darker and cyan that I have not yet seen in shaders. Don’t get me wrong, the shaders are awesome, they just miss that bit.

#6

I think that guy’s capture device is doing some of that rather it being a composite/NTSC issue, specifically. Here’s a shot of that same Sonic 3D Blast title screen on one of my PVMs hooked up via RGB:

4MhHDh6.jpg2048×1152
and here’s the same TV, same console, same camera with a composite connection:
hfUvxdQ.jpg2048×1152
As you can see, the colors are a little darker, the dithering is smeared and there’s the characteristic NTSC/composite artifacts, but the colors aren’t wildly different. That is, the red and magenta birds are pretty similar in both shots without any eye-searing glow, the yellows in the border are both still yellow, etc.

#7

Wow, yellow actually looks yellow on those shots!

But, some of the stuff that I spotted is there, well kinda, it’s just not wildly different as you said.

I guess the TV levels thing might be a reason for yellow not looking ochre. Green is darker in your composite shot and so are most dark colors, but hues look alike at glance. You may be right about the guy having something else going on in his setup.

I remember colors looking different back then but it could be faulty memory or maybe there is no “standard” colors, whatever it was, I realize it wasn’t for everyone sigh.