How Inkjet Printers Replicate the World of Colors

In recent years the price of home and home-office inkjet printers has declined dramatically. Unfortunately, the typical home user’s knowledge of color theory, color “spaces” and inkjet operation has not improved as much as the technology has, leading to continuing confusion about such things as “RGB,” “CMYK” and other such formerly arcane terms. A little remedial training in color theory is indicated.

The first thing most people learn (usually in grade school) about color is that there are three “primary” ones. But even this is a controversial area, as scientists describe the three as red, green and blue while art teachers call the primary colors blue, red and yellow. It is through combining these colors in various amounts that the full “gamut” of human-perceivable color can be created. For simplicity, the former is normally called the “RGB” color model and the latter “primary colors.”

Computers are confusing, too
The advent of the Information (Computer and Internet) Age has not helped clear up the confusion. The fact is, computer monitors operate on the RGB model, making the monitors themselves an “RGB color space.” But other technologies and processes use yet a third color model to create all the hues, the main one being the CMYK (Cyan, Magenta, Yellow, blacK) model used in printing.

Putting colors onto a readable surface (paper mostly) results in our reading off of reflective surfaces, bringing yet another variable into the color creation process. Over time it was discovered that breaking colors down into CMYK components resulted in the best approximation of human-perceivable colors, and that is the process used by color printers (on what are called “four-color” printing presses).

Printing at home
Home printers, however, cannot possibly operate like complex four-color presses, in which the paper is “hit” with four different printing plates carrying varying amounts of cyan, magenta, yellow and black inks. When combined in certain amounts, and at certain angles and resolutions, most colors are well replicated. However, the CMYK model has trouble with metallic and bright colors, which has led to the development of five- and six-color presses – CMYK plus the needed fifth and/or sixth color.

Inkjet printers for the home are Desktop inkjet printers are CMYK (hardware) devices. That is, the vast majority of them use four inks (Cyan, Magenta, Yellow, Black). It is important to remember that the goal of the consumer inkjet printer is not to replicate what comes off a commercial CMYK press, but to give consumers what they are accustomed to seeing in color photographic prints.

Therefore, the various manufacturers of such devices – Hewlett-Packard, Epson, Canon, Brother and dozens more – develop their own cyan, magenta, yellow and black inks that are capable of a wider color gamut, and are different from the standardized CMYK inks used in commercial printing. This means that they are CMYK output devices, despite the fact that printing from a computer means they have to handle the RGB color space also.

Going both ways
Some early inkjets (such as some HP Photosmart printers) were originally RGB output devices with those three ink colors, but most of today’s printers are CMYK output devices. However, unless you are converting your color spaces in Photoshop, you are most likely sending RGB information from your computer to your inkjet.

This means that the inkjet printers are generally set up to prefer RGB input that is then translated to the specific printer's CMYK color space by some sort of “proprietary conversion” that takes place at the “driver” stage. That is, when the print job is handled in the computer, the drivers (specific or generic) for that printer will do the color space conversion “on the fly” so that you don’t have to.

Summing up, then, the vast majority of today’s consumer inkjet printers are four-color (CMYK process) printing devices, but they prefer RGB input and can create more (and more brilliant) colors, across a wider gamut, than any other process currently in use.

Amazing machinery
Today’s computers, graphics software, monitors and inkjet printers perform a very complex task. As a “color production system,” together they create, mix and print virtually all the colors under the sun by combining the four CMYK inks. Some pretty heady, complicated science is involved in calculating how much of the various inks are required for what colors, how the ink drops are applied to the paper and what size the drops should be.

This is some impressive work going on. Remember, the computer and printer driver are working together to calculate all of the color conversion, and all of this is taking place while the print head is moving horizontally and the paper is moving vertically through the printer, at minute and precise intervals. The slightest error in math or movement, then, will result in wrong colors and spoiled prints.

This article is the merest of introductions to a fascinating and complex world, involving physiology, light, optics, computers and printing technology. You could make a career of studying any one of these topics, but the makers of inkjet printers for the home have to coordinate research and development while considering all of these variables. If color theory intrigues you, continue to read up on it and don’t forget to balance the art with the science to get the complete picture.