Wikipedia:Reference desk/Archives/Computing/2021 June 12

= June 12 =

Color 50% 50% 0%
We know that all these colors are:


 * Red = 100% 0% 0%
 * Yellow = 100% 100% 0%
 * Green = 0% 100% 0%
 * Cyan = 0% 100% 100%
 * Blue = 0% 0% 100%
 * Magenta = 100% 0% 100%
 * Black = 0% 0% 0%
 * White = 100% 100% 100%
 * Gray = 50% 50% 50%

However, what about 50% 50% 0%?? On the DOS computers of the early 90's it was kind of orange or brown; on Windows computers it is more olive green. Why this mismatch?? Georgia guy (talk) 23:51, 12 June 2021 (UTC)


 * I think it's to do with the type of graphics adapter. The 8-bit IBM CGA adapter with a 16-color palette did this sort of thing, which is 50-50-0 with 8 bits:
 * {| class="wikitable" align="left"

!style="color: black; background-color: #AAAA00;" colspan="2"|dark yellow
 * style="color: black; background-color: #AAAA00;" | 6
 * style="color: black; background-color: #AAAA00;" | #AAAA00
 * }
 * }


 * but RGBI monitors starting with the IBM 5153 with extra circuitry added some intensity to give this alternate brown:
 * {| class="wikitable" align="left"

!style="color: black; background-color: #AA5500;" colspan="2"|brown
 * style="color: black; background-color: #AA5500;" | 6
 * style="color: black; background-color: #AA5500;" | #AA5500
 * }
 * }


 * The Enhanced Graphics Adapter and later 16-bit adapters with a 64-color palette do this, which is 50-50-0 with 16 bits.
 * {| class="wikitable" align="left"

!style="color: white; background-color: #555500;" colspan="2"|olive
 * style="color: white; background-color: #555500;" | 48
 * style="color: white; background-color: #555500;" | #555500
 * }
 * }


 * MinorProphet (talk) 02:22, 13 June 2021 (UTC)
 * To make things (perhaps) a little clearer: as you note, Gray=50-50-50, but the intensity bit allows two shades of gray, 'dark white' and 'bright black' - see also List of monochrome and RGB color formats. These correspond to the 50-50-0 of dark yellow and olive in the examples above.
 * {| class="wikitable" align="left"

!style="color: black; background-color: #AAAAAA;" colspan="2"|Light gray
 * style="color: white; background-color: #AAAAAA;" | 7
 * style="color: white; background-color: #AAAAAA;" | #AAAAAA
 * }
 * }


 * {| class="wikitable" align="left"

!style="color: white; background-color: #555555;" colspan="2"|Dark gray
 * style="color: white; background-color: #555555;" | 8/56
 * style="color: white; background-color: #555555;" | #555555
 * }
 * }


 * MinorProphet (talk) 12:19, 13 June 2021 (UTC)
 * On a roll, now: the most legible contrast is something like this:
 * {| class="wikitable" align="left"

!style="color: #FFFF00; background-color: #0000FF;" colspan="2"|Cmd prompt
 * style="color: #FFFF00; background-color: #0000FF;" | #FFFF00
 * style="color: #FFFF00; background-color: #0000FF;" | on Blue
 * }
 * }


 * #0000FF skies, MinorProphet (talk) 13:14, 13 June 2021 (UTC)

The situation is a lot weirder than you think. See [ https://www.youtube.com/watch?v=wh4aWZRtTwU ]. Related: [ https://www.youtube.com/watch?v=uYbdx4I7STg ]. --Guy Macon (talk) 17:30, 13 June 2021 (UTC)
 * , that channel is priceless! Thanks for thinking of it! Elizium23 (talk) 17:34, 13 June 2021 (UTC)


 * In RGB, 50% is 80 in hex, so (50%, 50%, 0%) is #808000 — #808000 — GhostInTheMachine talk to me 18:51, 13 June 2021 (UTC)


 * Good catch! After the sun goes down, I am going to try the experiment from the above video; viewing that greenish-brown or brownish green (to my eyes) #808000 box on a black background in a dark room. Will become orange as the video predicts?


 * Some older monitors (and some image formats?) show a noticeable difference between #7F7F00 and #808000. --Guy Macon (talk) 22:30, 13 June 2021 (UTC)


 * Although they have been quite rightly reverted, I would like to apologise for my previous intemperate and ill-judged comments, which were out of place. Sorry. MinorProphet (talk) 02:09, 14 June 2021 (UTC)
 * Despite the fun and games with the brown sticky stuff (which you apparently can't see anyway), is anyone going to actually respond to the OP's question with a concise and technically correct answer? I'm itching to find out. MinorProphet (talk) 07:28, 14 June 2021 (UTC)
 * Isn't the answer given in : "Color 6 is treated differently; when using the formula above, color 6 would become dark yellow, as seen to the left, but in order to achieve a more pleasing brown tone, special circuitry in most RGBI monitors, starting with the IBM 5153 color display, makes an exception for color 6 and changes its hue from dark yellow to brown by halving the analogue green signal's amplitude."? (Essentially the first part of your first reply, except that this is a 4-bit colour space, not 8-bit.) --Lambiam 09:52, 14 June 2021 (UTC)
 * And within that colour space, there was no such thing as 50% 50% 0% or #808000. Expressed in hexadecimal, each of the RGB bytes was either #00, #55, #AA, or #FF. Moreover, except for the exceptional treatment of color 6, either all three bytes were even, or all three were odd. That leaves 16 possibilities. The closest to #808000 in that space was #AAAA00, which was changed to #AA5500. --Lambiam 10:16, 14 June 2021 (UTC)
 * Thank you. I was talking about an '8-bit adapter', which as you say only uses 4 bits for the color space: I was aware that my answer was somewhat imprecise. I used try to program the Intel 8051 UART serial adapter with Intel 8086 assembler, making up my own cables etc., but I have forgotten 98% of it except how much fun it was. I used to get paid for this sort of thing, but after a stroke some years back the details have become a little hazy. Maybe I shouldn't attempt to answer this sort of question any more. Suggestions on the back of a DIP module, please. MinorProphet (talk) 13:53, 14 June 2021 (UTC)