If you have worked with the Gamma control panel for any length of time you will begin to appreciate its weaknesses. It is difficult to visually calibrate a number of different workstations, manned by different personnel, consistently because everybody sees things a little differently. So, although a given monitor calibration can work for the person usually stationed at that computer another person may not be as accurate on that computer because they are used to a slightly different look in the monitor. Also, I'm convinced that one's visual color bias changes from day to day and from hour to hour. Add into the mix that maybe you stayed out too late last night or are otherwise fatigued and this can change the way you see colors and the way you calibrate. Thus, its almost impossible to calibrate with complete consistency.

Enter the hardware calibrator- a small photoelectric device that attaches to the front of the monitor with a suction cup and measures the actual output of the monitor. By comparing the measured output of known values a compensating color lookup table (clut) is generated and is then used to re-map the output to match the expected values. Most calibrators can now save Colorsync profiles for the monitor which can be used in a more comprehensive color management system.

The current hardware calibration system of choice is Color Vision's Optical software with X-rite's DTP92 Colorimeter . Color vision also has less expensive software called Photocal which can be used with their mc7 calibrator . X-rite also has a kind of general purpose color software called ColorShop which can be used with its calibrator for monitor calibration. Another alternative is ColorBlind Prove-it. Besides offering hardware calibration with a number of calibrators, it has a very robust visual calibration procedure and the software by itself is very inexpensive.