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Free color conversion tool from FireSprint.com

Discussion in 'General Chit-Chat' started by FireSprint.com, Sep 22, 2020.

  1. FireSprint.com

    FireSprint.com Trade Only Screen & Digital Sign Printing

    • Like Like x 7
  2. Christian @ 2CT Media

    Christian @ 2CT Media Major Contributor

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    Lab values are important too, but this is a great tool
     
    • Agree Agree x 1
  3. FireSprint.com

    FireSprint.com Trade Only Screen & Digital Sign Printing

    Good idea! Do you know if there is a chart somewhere?
     
  4. SignMeUpGraphics

    SignMeUpGraphics Moderator

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    Weird, it cuts off some of the values at our end. Latest Firefox, Chrome and Edge builds:

    upload_2020-9-23_10-59-46.png

    Edit: It's only occurring on our design PC... not others. Bizarre.
     
    • OMG / Wow! OMG / Wow! x 1
  5. Christian @ 2CT Media

    Christian @ 2CT Media Major Contributor

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    Let me look!
     
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  6. myront

    myront CorelDRAW is best

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    More in need of a paint code converter. Sherwin Williams and Benjamin Moore.
     
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    • Agree Agree x 1
  7. ColorCrest

    ColorCrest Active Member

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    I recommend the converter tool be upgraded to reference the latest Pantone Color Bridge values. Know that to trust the values precisely, the printer requires calibration to G7 standards (gray balance as the foundation) which the Bridge values are based and known color spaces such as sRGB (currently). The older Solid Coated values are long obsolete.

    BTW, Pantone does not transparently publish Lab values, mainly because they’re liable to change frequently. (Pantone may update any value at any time.)
     
    • Informative Informative x 1
  8. Christian @ 2CT Media

    Christian @ 2CT Media Major Contributor

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    This is the math:

    Adobe RGB to XYZ
    //aR, aG and aB (RGB Adobe 1998) input range = 0 ÷ 255
    //X, Y and Z output refer to a D65/2° standard illuminant.

    var_R = ( aR / 255 )
    var_G = ( aG / 255 )
    var_B = ( aB / 255 )

    var_R = var_R ^ 2.19921875
    var_G = var_G ^ 2.19921875
    var_B = var_B ^ 2.19921875

    var_R = var_R * 100
    var_G = var_G * 100
    var_B = var_B * 100

    X = var_R * 0.57667 + var_G * 0.18555 + var_B * 0.18819
    Y = var_R * 0.29738 + var_G * 0.62735 + var_B * 0.07527
    Z = var_R * 0.02703 + var_G * 0.07069 + var_B * 0.99110

    XYZ to LAB
    //Reference-X, Y and Z refer to specific illuminants and observers.
    //Common reference values are available below in this same page.

    var_X = X / Reference-X
    var_Y = Y / Reference-Y
    var_Z = Z / Reference-Z

    if ( var_X > 0.008856 ) var_X = var_X ^ ( 1/3 )
    else var_X = ( 7.787 * var_X ) + ( 16 / 116 )
    if ( var_Y > 0.008856 ) var_Y = var_Y ^ ( 1/3 )
    else var_Y = ( 7.787 * var_Y ) + ( 16 / 116 )
    if ( var_Z > 0.008856 ) var_Z = var_Z ^ ( 1/3 )
    else var_Z = ( 7.787 * var_Z ) + ( 16 / 116 )

    CIE-L* = ( 116 * var_Y ) - 16
    CIE-a* = 500 * ( var_X - var_Y )
    CIE-b* = 200 * ( var_Y - var_Z )
     
    • Informative Informative x 1
  9. Christian @ 2CT Media

    Christian @ 2CT Media Major Contributor

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    If using sRGB
    //sR, sG and sB (Standard RGB) input range = 0 ÷ 255
    //X, Y and Z output refer to a D65/2° standard illuminant.

    var_R = ( sR / 255 )
    var_G = ( sG / 255 )
    var_B = ( sB / 255 )

    if ( var_R > 0.04045 ) var_R = ( ( var_R + 0.055 ) / 1.055 ) ^ 2.4
    else var_R = var_R / 12.92
    if ( var_G > 0.04045 ) var_G = ( ( var_G + 0.055 ) / 1.055 ) ^ 2.4
    else var_G = var_G / 12.92
    if ( var_B > 0.04045 ) var_B = ( ( var_B + 0.055 ) / 1.055 ) ^ 2.4
    else var_B = var_B / 12.92

    var_R = var_R * 100
    var_G = var_G * 100
    var_B = var_B * 100

    X = var_R * 0.4124 + var_G * 0.3576 + var_B * 0.1805
    Y = var_R * 0.2126 + var_G * 0.7152 + var_B * 0.0722
    Z = var_R * 0.0193 + var_G * 0.1192 + var_B * 0.9505
     
    • Informative Informative x 1
  10. Jester

    Jester Slow is Fast

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    I'll start by admitting I'm a color neophyte, but How can this be? If CIE L*a*b* is a device-independent descriptor of color then, if what you say is true, specifying a Pantone color would not give a consistent visual result over time. Wouldn't this defeat the entire purpose of a color standard?
     
  11. ColorCrest

    ColorCrest Active Member

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    Pantone colors are somewhat of a moving target. (One reason they advise replacing swatch books every year.) They modify values any place they need to better print a certain number of individual colors on a single press sheet. (I forget the count and sheet size.) Not an easy feat.

    I suppose if Pantone were a conventional "color space," which it is not, Lab values could remain constant. In practice, I doubt if anyone would ever notice different Lab values effects. I think there are other for more noticeable effects from other parameters, especially workflow settings and press calibration.
     
  12. Jester

    Jester Slow is Fast

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    So.... I've always found this strange:
    • Pantone doesn't publish L*a*b* values, which are device independent descriptors of color.
    • But Pantone publishes CMYK values, which are changed annually when they publish a new book because they are device-dependent (as I understand it, the published values are from their own in-house production processes);
    • and Pantone publishes RGB values, which are again a 'variable standard' of color which depends on the defined observer, of which there are many standards even among those promulgated by CIE.
    I understand that color is a subjective science [oxymoron], but doesn't this seem just a little bit like a case of "the emperor has no clothes"?
     
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  13. ColorCrest

    ColorCrest Active Member

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    What's important is to understand the color working space(s) where one would reference the published color values and let the downstream RIP interpret those using a (now known be G7 calibrated) printer. The latest Bridge is the best we've been offered. Beforehand, not so much.

    It would be helpful if the color conversion tool provided the necessary working space(s) and, in the case of CMYK, the necessary output space. Only with the latest Bridge is that information available as opposed to earlier.

    Also know that radically different Lab values may produce colors perceptually matching both onscreen and in print.
     
  14. Christian @ 2CT Media

    Christian @ 2CT Media Major Contributor

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    You understand why this is right? 1 or Both Devices are out of spec. All colorspaces will exhibit this, but, LAB is a device-independent absolute color coordinate. If that color is not displayed correctly, LAB is one of the few targets that a device can be actually mapped too, or defined as unreproducible.

    The importance of LAB is that it has a center point of "perfect" grey which is the absence of color and an even absorption and radiation of light, the ideal target of the G7 method.
     
  15. ColorCrest

    ColorCrest Active Member

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    Well, no. It has to do with the scale of Lab and the limited perception of distinguishable colors of human vision. (Not to mention the limited colors that typical displays and printers produce.)

    The common color spaces of sRGB, Adobe RGB (1998), ProPhoto and some others all have their neutral centers of grays, black through white. So, Lab is not alone.
     
  16. Christian @ 2CT Media

    Christian @ 2CT Media Major Contributor

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    Those 3 color spaces are device dependant. They describe color as a additive process from black. That is limited to a device type that starts at black. Printers do not, they are a subtractive process. LAB is an exactly defined color coordinate that can be made via Additive or Subtractive processes.

    Yes their center is Grey, but absolute 0 in LAB is Perfect Gray/Grey. In RGB absolute 0 is Black or the total abortion of light.
     
  17. FireSprint.com

    FireSprint.com Trade Only Screen & Digital Sign Printing

    I will fully admit you guys know far more about this than I do. It's been fascinating reading through this! The tool I built simply relies on what Pantone lists as the appropriate CMYK, RGB and HEX values for their colors. Right off their website. It was fairly easy to create so I made it in hopes it would help a few people out. Just a little bit faster way to get the approximate color data they need.

    Still, I mean it! Fascinating! 99% of the people walking around think they understand color, and I guess in a way they do, but not like this. :)
     
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  18. ColorCrest

    ColorCrest Active Member

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    Actually, RGB absolute black is the absence of light. Also, there are no devices on the planet which can reproduce the imaginary colors of the ProPhoto color space.

    However, I don't see how this tangent is helping the OP or the users of the color conversion tool which should be updated to the current methods and technology. IMO, is all.
     
  19. jochwat

    jochwat Graphics Department

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    [QUOTE="Still, I mean it! Fascinating! 99% of the people walking around think they understand color, and I guess in a way they do, but not like this. :)[/QUOTE]

    What I understand about color is that my favorite one is purple.
     
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  20. Boudica

    Boudica Member

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    This is cool! My work around has always been to use photoshop to type in the pantone number, then I switch to the picker and see what the cmyk value is.
     
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