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- A hardware device to calibrate monitors -

Summary: Computer monitors need to be adjusted, or calibrated, for white and black set points and neutral color. Once adjusted a monitor profile can be used to "tell" graphic software and printers about how your monitor displays colors. A device called a colorimeter is used to to precisely measure screen colors during calibration.

Jack DeAngelis, PhD
OSU Ext. Entomologist (ret.)

There are three separate procedures that you should perform to get the best possible results from your computer monitor. These are: (1) adjusting the black and white set points; (2) color cast removal; and (3) monitor profiling.

While procedures 1 and 2 may be preformed "by eye" they are much more accurately done with a device called a colorimeter. Steps 1 & 2 are sometimes called pre-calibration. Monitor profiles, step 3, however, can only be constructed using a colorimeter and appropriate profiling software.

Black and White Set Points - Have you ever used a monitor that appeared to be too dark, or too light, to clearly see detail? This is usually a problem with black or white set points or contrast and brightness in old TV lingo. These adjustments can often be done inexpensively by eye (see Related Articles below).

Color Cast Removal - A color cast occurs when a neutral grey subject appears to have a color, usually green, red or blue. If your monitor is displaying a color cast you'll never be able accurately see true colors on screen until it is removed. Slight color casts can only be removed using a colorimeter but large color casts can sometimes be partially removed by eye.

Monitor Profiles - The final step is to create a computer file that tells other programs, like image editors such as PhotoShop, how your monitor displays colors or shades of grey. These programs can then use the information to electronically adjust an image whenever they display one that has an "embedded" profile.

This final step is called profiling. Profiling is critically important for photography and graphic arts, but less important for the average user. Printers can, and should, be profiled as well. Profiles are generated by software from light intensity data collected by colorimeters.

All of these procedures depend on being able to accurately measure small differences in color and light intensity coming from a monitor. Human eyes are not very good at this because our perception of color and light intensity is strongly influenced by many external factors. Light meters are much better because the extraneous factors can be filtered out. Light meters that can measure the intensity of specific colors of light are called colorimeters.

In use the colorimeter is attached to the monitor screen by suction cups. Software then guides you through the process of pre-calibration, calibration and profiling. The whole process is fairly simple and re-calibration needs to be done only about once a month.

Related Articles

Inexpensive Eye-based Monitor Adjustments

What is Computer Monitor Calibration?

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