Subject: Re: [stella] tia hue luminance From: Adam Wozniak <adam@xxxxxxxxxxxxxxxx> Date: Thu, 11 Dec 2003 08:11:17 -0800 (PST) |
On Wed, 10 Dec 2003, Glenn Saunders wrote: > 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. Eric Ball's equations yeild #000000 for col=0,lu=0 (blackest black) and #A0A0A0 for col=0,lu=7 (whitest white). Before your post, I would have expected them to range from #000000 to #FFFFFF, because I'm a sort of an algorithmic purist. But now I see we're trying to emulate real hardware, or idealized real hardware, or some similar critter, and I have no clue what to expect. > 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. Which makes it even worse. -- adam@xxxxxxxxxxxxxxxx http://cuddlepuddle.org/~adam/pgp.html Will code for food. http://cuddlepuddle.org/~adam/resume.html "The dinosaurs are not around today because they did not have a space program." -- Arthur C. Clarke ---------------------------------------------------------------------------------------------- Archives (includes files) at http://www.biglist.com/lists/stella/archives/ Unsub & more at http://www.biglist.com/lists/stella/
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