Complexity of Color - Part 2

Last time we took a brief look at how we see color with our naked eye, and how that color differs when viewed on a monitor.
This time we'll take a brief look at how the colors we see on the monitor relates to the colors that are able to be reproduced by the printing process. I am purposely skipping the proofing process; that "preview" of what the final printed product will look like because, quite frankly, it can be a real pain. And, it might be easier to see why once you see how color images are printed on paper.
We saw that a monitor reproduces color by an additive process: by combining the 3 colors red (r), green (g), and blue (b), or rgb. In the basic 4 color process printing method, four (you guessed it!) colors of inks are used: cyan, magenta, yellow, and black (represented by "k"), or "cmyk". The inks are semi-transparent, and the colors reproduced by putting the inks on paper use a subtractive means; each color subtracts something from the white color of the paper; and also an additive means. The images are printed as dots of ink, and the closeness of the dots produce colors by additive blending.
Just as the same image viewed on different monitors will look different due to monitor calibration, different printers or even the same printer using different equipment or paper (coated, uncoated, gloss, matte, etc.) can end up with color variations of the same image represented here by the rounded triangles on this image:



Combining the color gamuts (your phrase for today: the available color space exhibited by a unique color device.) gives us this comparison:



where the triangle defines the color spectrum you can see on your monitor, and the rounded triangle defines the color spectrum that can be reproduced with printing inks on paper.
So you can see where problems may arise when someone, oh, say a publisher, editor, or even a designer, sees a printed piece and politely exclaims "that's not the way it looked on my monitor!"

Hence the need for color accurate proofs before the printing process begins. A subject for another time.

© 2005, Bob Cooper

Complexity of Color - Part 1

At first glance, it would appear that color is a pretty simple concept. You look at grass, and it's green. You look at a (red) rose, and it's red, right? The complex part comes when you want to take what you see and end up with a printed product accurately reflecting the image you see with your eyes. The color spectrum visible to the human eye is represented by this image:

Devices used to capture an image (film in a camera, the scan of that film, a digital camera image) have a more limited ability to "see" the colors. Once the image is digitized and viewed on a computer monitor, it is an rgb (red, green, blue) image. That is, all the colors you see on a monitor are made up by varying the luminosity of those three colors. For example, all three colors "switched" off gives you black. All three colors displayed at their maximum intensity make white. All the colors inbetween are produced by the blending of these three colors at varying brightness that takes place at the viewer's retina. Color produced this way is known as an additive mixture. The triangles in this image:

represent the color spectrum able to be reproduced by two different monitors compared to what the human eye can see. As you can see, not only is the reproducable color spectrum much smaller than the human eye can see, different monitors will vary in their display of the digital image depending on the monitor calibration.

Enough for the exiciting introduction... Next time I'll discuss proofing and printing methods and some challenges inherent in reproducing color images on paper.

© 2005, Bob Cooper