Why What you See Is Not Always What You Get

19 Oct

Color management is probably one of the most confusing and difficult challenges facing the design staff of any firm.  Frankly, its one of those things that rarely gets adequately explained.  We think of it like roller skating.  It looks simple.  But when you strap the skates on for the first time and start barreling down the steepest hill you can find, things are about to get a little out of control.

So, let’s eliminate some of the mystery.  Just keep in mind, in many ways this will be like learning to skate or ride a bicycle.  So, we’ll start simple and build up speed gradually.

Way back in 1942, a gentleman by the name of Richard Hunter came up with a 3-dimensional coordinate system Called LAB.  LAB was a fairly successful attempt to describe and quantify the way the human eye perceives color.  The common model for LAB is represented by a sphere with the axis: L, a and b. The L axis has a range of 0 to 100 and defines the amount of white or black (depending on your point of view).  The a axis ranges (in Photoshop) from -128 to +127.  Positive numbers describe the amount of red and negative numbers describe the amount of green.  The b axis ranges (in Photoshop) from -128 to +127.  Positive numbers describe the amount of yellow and negative colors describe the amount of blue.

So what does this have to do with the real world?  To put it simply, LAB or more accurately CIE/LAB is the universal language for all print devices.  No matter what you build your file in (Photoshop, Illustrator, Corel Draw or Powerpoint) at some point all the digital color information is going to be converted to CIE/LAB for printing.

Now here’s one of the places color gets misleading.  Your computer monitor displays in a different color space called sRGB (to be precise your monitor probably displays in sRGB IEC61966-2.1).  This monitor profile was created by HP and Microsoft for color monitors.  The idea was to establish a global base line for display of color images over the web.  Color on your monitor is produced by exciting three different types of photosphere channels: red green and blue.  If all three channels are maxed out you get white light.  Conversely, if all three channels are completely suppressed you get black.

But wait there’s more!  Your computer display is governed by something called a CLUT. That’s an acronym for “Color Look Up Table”.  If your system is new, everything should be fine since all of the drivers are current and your hardware is new and running off of what amounts to factory presets.  However if your monitor has been around a few months, it might be a good idea to update your profile.  Unless you are doing critical Photoshop retouch, you can probably manage by using the operating system to update your display.  It’s also a good idea to keep your monitor updated because that also allows your system to keep the CLUT current.

Just for the sake of argument.  Let’s say you’re just working with a small desktop printer on your home system.  You build your art and your system displays the color values in sRGB IEC blah, blah, blah.  That display is referenced against the CLUT by your operating system.  You like what you see and you decide it’s time to hit print.  Now the hidden world of mad calculations kicks into gear.  Your operating system, the printer drivers, your graphics card and your application all interact to create and send a print file to your printer.  They work together to calculate the CIE/LAB equivalents of your RGB colors and then tell the printer what to print in the printers own language.  Now you look at your printed piece and most of the art looks right.  But some of the colors don’t appear quite the way you wanted.  What happened?

What has likely happened is some of your art has been created with colors that are outside of the gamut (the range of colors within the ability of a device to reproduce) of your printer.  Remember when we described the Lab color model as a sphere?  If the abilities of your printer were measured against Lab space it’s shape might better resemble an extra-large, jelly donut.  Lab (or at least the amount of Lab space available to your system and the software you’re employing) is an NBA basketball in comparison.  In essence, the creation of a printer file is an attempt to take that NBA basketball and stick it in the extra large jelly donut.  It is almost inevitable that something will get lost in the translation.

Is this the whole picture?  Afraid not.  Come back for the next installment and will take a more in-depth look at print file creation.

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2 Responses to “Why What you See Is Not Always What You Get”

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  1. Constructing a Bullet-Proof Digital File with Illustrator « BPI Inc. - July 17, 2012

    […] you’ve never visited this blog before, perhaps you should visit some of our other postings: “Why What you See Is Not Always What You Get!”; “Basketballs, Meatloafs and Frisbees, Oh My!”; and, “Those Pesky […]

  2. Constructing a Bullet-Proof Digital File with InDesign « BPI Inc. - October 9, 2012

    […] If you’ve never visited this blog before, visit some of our previous postings: “Why What you See Is Not Always What You Get!,” “Basketballs, Meatloafs and Frisbees, Oh My!,” and “Those Pesky […]

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