<page xmlns="http://projectmallard.org/1.0/"
      type="topic" style="question"
      id="color-whyimportant">

  <info>
    <link type="guide" xref="color"/>
    <desc>Color management is important for designers, photographers and artists.</desc>
    <credit type="author">
      <name>Richard Hughes</name>
      <email>richard@hughsie.com</email>
    </credit>
    <include href="legal.xml" xmlns="http://www.w3.org/2001/XInclude"/>
  </info>

  <title>Why is color management important?</title>
  <p>
    Color management is the process of capturing a color using an input
    device, displaying it on a screen, and printing it all whilst managing
    the exact colors and the range of colors on each medium.
  </p>

  <p>
    The need for color management is probably explained best with a
    photograph of a bird on a frosty day in winter.
  </p>

  <figure>
    <desc>A bird on a frosty wall as seen on the camera view-finder</desc>
    <media type="image" mime="image/png" src="figures/color-camera.png"/>
  </figure>

  <p>
    Displays typically over-saturate the blue channel, making the images
    look cold.
  </p>

  <figure>
    <desc>This is what the user sees on a typical business laptop screen</desc>
    <media type="image" mime="image/png" src="figures/color-display.png"/>
  </figure>

  <p>
    Notice how the white is not 'paper white' and the black of the eye
    is now a muddy brown.
  </p>

  <figure>
    <desc>This is what the user sees when printing on a typical inkjet printer</desc>
    <media type="image" mime="image/png" src="figures/color-printer.png"/>
  </figure>

  <p>
    The basic problem we have here is that each device is capable of
    handling a different range of colors.
    So while you might be able to take a photo of electric blue, most
    printers are not going to be able to reproduce it.
  </p>
  <p>
    Most image devices capture in RGB (Red, Green, Blue) and have
    to convert to CMYK (Cyan, Magenta, Yellow, and Black) to print.
    Another problem is that you can't have <em>white</em> ink, and so
    the whiteness can only be as good as the paper color.
  </p>

  <p>
    Another problem is units. Without specifying the scale on which a 
    color is measured, we don't know if 100% red is near infrared or 
    just the deepest red ink in the printer. What is 50% red on one 
    display is probably something like 62% on another display. 
    It's like telling a person that you've just driven 7 units of
    distance, without the unit you don't know if that's 7 kilometers or
    7 meters.
  </p>

  <p>
    In color, we refer to the units as gamut. Gamut is essentially the
    range of colors that can be reproduced.
    A device like a DSLR camera might have a very large gamut, being able
    to capture all the colors in a sunset, but a projector has a very
    small gamut and all the colors are going to look "washed out".
  </p>

  <p>
    In some cases we can <em>correct</em> the device output by altering
    the data we sent to it, but in other cases where that's not
    possible (you can't print electric blue) we need to show the user
    what the result is going to look like.
  </p>

  <p>
    For photographs it makes sense allowing a relative shift of all 
    colors to match color reproduction capabilities of a display or a 
    printer, therefore you need to be able to access full tonal range of 
    that display or printer. For other graphics such as logos you simply 
    don't use the full tonal range, you only need few colors matching as 
    closely as possible, so if you're trying to print a custom mug with 
    the Red Hat logo, that <em>has</em> to be the exact Red Hat Red. The 
    method of transferring colors from one tonal range to another is 
    usually called gamut mapping.
  </p>

</page>
