Re: [stella] tia hue luminance

Subject: Re: [stella] tia hue luminance
From: Glenn Saunders <mos6507@xxxxxxxxxxx>
Date: Wed, 10 Dec 2003 22:33:36 -0800
At 08:05 AM 12/10/2003, you wrote:

The only way to get a true white for col=0 lu=7 is to use a ypmult >= 1/14.
This tends to wash out the other colors though.

What do you consider a true white?

I know from my Toaster/Flyer days that you can't generate a video-legal RGB 255,255,255. The top end of composite video is something around 190-220 or so. I can't remember the actual cutoff. Beyond that it generates IRE values above the legal threshold.

NTSC has a compressed colorspace and therefore can not generate a full 24-bit display. The blacks are not true black and the whites are not true white. I think the blackest black in NTSC is something around 34,34,34.

I think the difference between NTSC for north america and japan is the IRE 0 floor. I think in Japan it's set at RGB 0,0,0. This is something the average television viewer might not notice but something you can see on a vectorscope.

So going from an idealized digital RGB to NTSC always involves some losses, whereas you can represent an NTSC image in RGB okay.

Now, it's been stated on multiple occasions that the 2600 doesn't generate a totally in-spec NTSC signal so I'm not sure if its blackest black and its whitest white even conforms to NTSC guidelines.

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