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Indistinguishable Colors — Parallax Forums

Indistinguishable Colors

Vega256Vega256 Posts: 197
edited 2013-01-02 12:22 in Propeller 1
Hey,

While looking at the Prop's full color gamut, I noticed that colors with luma values 4 and 5 are indiscernible and/or are the same color altogether. Does anyone know why this is, and perhaps a solution?

Comments

  • whickerwhicker Posts: 749
    edited 2012-12-29 15:38
    The simple way of producing color TV on the Propeller involves only changing what is essentially the hue of the color and the overall brightness of that color. There is still one other main variable and that is saturation (how strong or weak the color is). The resistor circuit doesn't account for this.

    Once a particular hue gets bright enough (over 30%), yes, visually to us variations in brightness don't look that much different. Also, TV's aren't linear in their signaling, either (equal steps up or down do not produce equal changes in visible brighness).

    There are many ways to produce color television. The point is how involved do you want it to be, what your end goal is, and how many other people besides yourself would bother to build the circuit if you wanted other people to try your game or software?
  • Vega256Vega256 Posts: 197
    edited 2012-12-31 06:45
    I can tell the difference in colors with luma values 3 and 6; only the values in between give me the "same" color. In the end result, I would like to have a computer video system with a relatively large palette. If all of the colors I am getting were unique, I would be getting 65 colors in total. Since I noticed that two colors were actually one, I only actually have 49 colors; in this application, the extra 16 colors are important.
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2012-12-31 09:22
    It might be that your resistor DAC uses the wrong values and is causing saturation. See this thread:

    -Phil
  • Vega256Vega256 Posts: 197
    edited 2012-12-31 09:34
    Phil Pilgrim (PhiPi) wrote: »
    It might be that your resistor DAC uses the wrong values and is causing saturation. See this thread:
    -Phil
    Thanks, Phil. I'll give it a try, and post back.
  • potatoheadpotatohead Posts: 10,261
    edited 2012-12-31 09:41
    TV or VGA?

    It could also be the display is "crushing" the luma values. Some displays have a gamma setting that can cause this. If VGA, check that. If TV, are you using a newer TV or older CRT one? And are you using RF modulator or straight composite connection?

    I suspect the resistors too, but it could be a display thing. Try various adjustments and or a "factory" mode, if the display has one.

    This can happen in the driver too. Are you running a Parallax one, or a custom one? Which one?
  • Vega256Vega256 Posts: 197
    edited 2012-12-31 09:50
    potatohead wrote: »
    TV or VGA?

    It could also be the display is "crushing" the luma values. Some displays have a gamma setting that can cause this. If VGA, check that. If TV, are you using a newer TV or older CRT one? And are you using RF modulator or straight composite connection?

    I suspect the resistors too, but it could be a display thing. Try various adjustments and or a "factory" mode, if the display has one.

    This can happen in the driver too. Are you running a Parallax one, or a custom one? Which one?
    I'm using an older CRT TV, straight composite connection. This is a custom driver.
  • potatoheadpotatohead Posts: 10,261
    edited 2012-12-31 10:36
    I would run the graphics demo one as a quick test. Define a few tiles with the various lumas and see whether or not they perform the same.
  • Vega256Vega256 Posts: 197
    edited 2013-01-02 12:22
    Phil Pilgrim (PhiPi) wrote: »
    It might be that your resistor DAC uses the wrong values and is causing saturation. See this thread:
    -Phil
    About your DAC, Phil, which of the three pins are the video pins? What is the fourth pin for?
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