One of the keys to getting good, consistent image quality lies in maintaining a calibrated workflow.  In this article I will discuss some of the myths and truths about color calibration, what it is and what you can expect to get from it.

What is Color Calibration?

Let's start by first defining what color calibration is.  Color calibration is the process of adjusting the output devices of the digital workflow so that the colors remain consistent from monitor to print.

To begin with, we'll discuss the characteristics of color itself.  Technically, color doesn't exist.  It is an illusion created by the cones in our eyes.  To verify this, simply open any digital image in your image program of choice and view the individual color channels.  You'll notice they're all greyscale.  I won't go any further into the details of this because I don't really know the details and because you don't need to understand them in order to grasp the concept of color calibration.

There are two types of light: reflective light and transmissive light.  Reflective light is light that is reflected off of objects, while transmissive light is actually created or transmitted by the object itself.  A photographic print is an example of a reflective light source because in order for us to see it we need to have it illuminated by a light source.  We see the colors in the print because certain areas of the print reflect different "colors" of light into our eyes.  A good example of a transmissive light source is a computer monitor.  A monitor creates red, green and blue light and combines them together to produce all the colors in the visible spectrum.

I'm Seeing Blue, I Think

Let's say you're viewing a picture taken during a nice sunny day on your monitor.  The sky appears blue.  But just exactly what shade of blue are we looking at?  Your first reaction would be to think, "Well, that's easy.  It looks light blue so I must be seeing light blue."  But are you really?  If you were to take that image and display it on a different monitor--say the monitor of your Uncle Bob who only uses his computer to sell insurance--chances are that light blue sky is going to appear a slightly different shade of blue.  Why?  Because each monitor manufacturer has its ideas about how the various colors should appear.  In order to get our monitors to actually display the color blue as defined by a known standard, we need to calibrate it.   Of course, this applies to the entirety of the 16.7 million colors that most monitors can display, not just blue.  Once calibrated, we can be sure that our computer screens are actually displaying colors as they were meant to be seen.

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How Will Calibration Help Me?

Calibration will help you acheive the desired look you want from your final prints much easier.  Although a print won't match the image you see on your monitor, calibration will allow you to get predictable results.  You're probably asking yourself how predictable results can possibly be helpful.  After all, don't we want to know exact results so we know exactly how are prints will look on paper?  In an ideal world, we could get exact results, but unfortunately we have to work within the limits of current technology and the fact that it's just not physically possible to have a reflective light source (the print) match a transmissive light source (the monitor) because of the way they display colors.

By getting predictable results, we can know how to alter the image on the monitor so that we can get our print looking the way we want to.  Because we know that our monitor is properly calibrated, that's one less variable in the work process that we have to worry about.  As an example, say you make a proof print and you find out that the foliage in your image isn't as green as you'd like it to be.  Without a color calibrated monitor, how would you know how to adjust the image you see on screen to get the desired color?  How is the monitor displaying colors?  Are the greens you see on the monitor truly green or is there some color cast to them?  How do you alter the colors in the image to get the desired results if you have no base point to start with?  With a color calibrated monitor, if your print has greens that aren't saturated enough, it's then a simple matter of adjusting the saturation until your proof print has the desired look that you're trying to acheive.

Methods of Monitor Calibration

There are two primary ways of calibrating your monitor: visually or by using special hardware and software.  Although both methods use software, the visual method is not nearly as exact as the hardware/software combination.  Visually calibrating your monitor involves looking at predefined test patterns and adjusting the various monitor settings until the test appear as instructed within the software.  A classic example of this type of software is Adobe Gamma.  As of Photoshop CS3 this program no longer ships with Photoshop but it might still be available separately on the internet. 

The better method, and the one that I use, is to use a special hardware device called a colorimeter along with the proper software for it.  The colorimeter (or "puck") is a special optical device that is placed on your monitor screen.  The software displays a series of color swatches on the monitor which the puck reads and compares them with what the color values should be.  Based on this information, it alters your computer's graphics card look-up table (or LUT) so that your graphics card displays the proper colors.

Recommendations

While I haven't used all of the monitor calibration packages listed here, I am including them because these are the more common packages that tend to be used for color calibration.  They are listed in no particular order.

• Datacolor Spyder3 series of calibration packages
• X-Rite (formerly Gretag Macbeth) i1 Display2 and i1 Lite
• Color Eyes Display Pro by Integrated Color (this is what I use)