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Thread: gettin a handle on r g b on a color laser and etherdream...

  1. #11
    Join Date
    Nov 2017
    Location
    Seattle, WA
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    97

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    well, for SOME reason things seem to be working out for me color wise.

    although i've done nooothin.

    the regular n*32767/255 seems to work basically.

    and for my testing where the laser is right next to an unhuge canvas,
    i'm using n*8191/255 cuz at full brightness my eyes feel weird.
    I'm guessing at that short distance, even the reflections off the canvas
    (a regular oil painting canvas) is pretty dang bright.

    when i use 4095 the colors go weird.
    prob cuz at low brightness levels the variances get too wide.

    well, i would still appreciate a decent logarithmic scale from
    0..32767 (or how to calc it).

    thanks for tryin tho yall.

  2. #12
    Join Date
    Jul 2008
    Posts
    453

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    Quote Originally Posted by stephenhazel View Post
    well, for SOME reason things seem to be working out for me color wise.

    although i've done nooothin.

    the regular n*32767/255 seems to work basically.

    and for my testing where the laser is right next to an unhuge canvas,
    i'm using n*8191/255 cuz at full brightness my eyes feel weird.
    I'm guessing at that short distance, even the reflections off the canvas
    (a regular oil painting canvas) is pretty dang bright.

    when i use 4095 the colors go weird.
    prob cuz at low brightness levels the variances get too wide.

    well, i would still appreciate a decent logarithmic scale from
    0..32767 (or how to calc it).

    thanks for tryin tho yall.
    Try this for log scale:

    For an input range 0-255 and an output range of 0-MaxOut:

    Multiplier = MaxOut/LOG(256)

    Output = LOG(Input + 1) * Multiplier

    In this particular case, the base of the log doesn't matter because the multiplier balances things out. The results are similar to a gamma of 4.
    Once milk has been poured over corn flakes, the clock starts ticking.

  3. #13
    Join Date
    Nov 2017
    Location
    Seattle, WA
    Posts
    97

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    Quote Originally Posted by dchammonds View Post
    Try this for log scale:

    For an input range 0-255 and an output range of 0-MaxOut:

    Multiplier = MaxOut/LOG(256)

    Output = LOG(Input + 1) * Multiplier

    In this particular case, the base of the log doesn't matter because the multiplier balances things out. The results are similar to a gamma of 4.

    Hmmm i will DEFINITELY give that a try.

    for (i = 0; i < 256; i++) o [i] = LOG(i+1)*32767/LOG(256);

    Seems weird that it leaps from 0,0 to 1,4095...

    But, i will giiiiiiiive it a shot !!

    thanks much, dude!

  4. #14
    Join Date
    Jul 2008
    Posts
    453

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    Quote Originally Posted by stephenhazel View Post
    Hmmm i will DEFINITELY give that a try.

    for (i = 0; i < 256; i++) o [i] = LOG(i+1)*32767/LOG(256);

    Seems weird that it leaps from 0,0 to 1,4095...

    But, i will giiiiiiiive it a shot !!

    thanks much, dude!
    Let me know how it turns out. I like the gamma model for its adjustability, but this form can be made adjustable too.
    Once milk has been poured over corn flakes, the clock starts ticking.

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