John B. Matthews wrote:
In article <es6dneorgaLqcSTVnZ2dnUVZ_gSdnZ2d@comcast.com>, "Michael J. Mahon" <mjmahon@aol.com> wrote:John B. Matthews wrote:<http://home.woh.rr.com/jbmatthews/a2/lores.html>I have a clear memory of the NTSC video red being a dark shade, as Linards suggests. I have no idea why the Applesoft manual calls it "magenta," which I identify with a secondary color having sRGB components (0xFF00FF). Of course, the html rendering is itself a function of the monitor's calibration.Color 1 has only one bit of four set, so its luminance value is 25% of white. The hi-res colors (not white and black) all have two bits set, and so have a luminance value of 50%, so lo-res color 1 is definitely a "dark" shade. (Note that 0xFF00FF has a luminance of 67%--very much a "light" color.Ah, thank you, Michael. This sheds light (no pun:-) on Linards' derivation, which matches my recollection. I remember the "yellow" being more of a gold and the "brown" being a muddy green, but I'd swear there were two different grays. I'm curious why his table shows the two grays, [5] and [A], having the same sRGB 0x808080. Is that that the difference in luminance, also?
No, the two grays are visually identical (though they may produce different artifacts when they border other colors). They are both devoid of any chroma, and both have 50% luminance. From a video signal point of view, they each are 7MHz waveforms, but of opposite phase. Since they contain no 3.58MHz signal, they do not produce any color. On a hi-res monochrome display, both have two white lines and two black lines, but one is WBWB ($A) and the other is BWBW ($5). -michael AppleCrate II: An Apple II "blade server"! Home page: http://members.aol.com/MJMahon/ "The wastebasket is our most important design tool--and it's seriously underused."