A profile is a snapshot of your device's color behavior at a certain point in time. To get the best results, your device should be in a stable and repeatable state. In theory, as long as your device never changes you should never need to re-profile. However, wear and tear on your device and environmental changes will cause color shifts over time, and re-profiling is the best way to correct this problem.

CRT Displays

Traditional cathode-ray tube displays will change over time due to burn-in, phosphor fading and diminished efficiency of the cathode and intensity of the electron beam. CRTs are also very sensitive to electro-magnetic fields and changes in power supply voltage. We recommend keeping speakers, motors and other monitors away from your profiled display to help reduce these effects. Variances in the line voltage supplied to your facility can also change the behavior of your display, so a line conditioner or uninterruptible power supply (UPS) is suggested.

• For the hobbyist, profiling once or twice a month should be sufficient.
• For individuals using their system frequently, we recommend profiling once a week.
• For professionals who rely on the accuracy of their display for their livelihood, we recommend profiling daily.

In general, it is safer to profile more frequently rather than less frequently.

LCD Displays

Liquid-crystal displays tend to be more stable than CRT displays because of their design. Each pixel is fixed in place rather than being  "painted" by an electron beam many times a second. This allows them to be more consistent and color displayed on one part of the display has less effect on the other areas. Furthermore, digitally connected displays, such as those using a DVI or ADC connector, are more consistent because the signal is less vulnerable to interference from surrounding equipment. However, the phosphors do still fade, as will the bulb in the back-light.

• For the hobbyist, profiling once or twice a month should be sufficient.
• For individuals using their system frequently, we recommend profiling once a week.
• For professionals who rely on the accuracy of their display for their livelihood, we recommend profiling daily. However, this may not be necessary with a digitally connected display.

For both LCD and CRT displays, the best way to determine how often to profile is with an accuracy test that can be repeated over time. To check the accuracy of your monitor with i1Match, go to the Help menu on a PC or the Eye-One Match menu on a Mac and choose "Start Monitor Validator". Follow the instructions to measure the colors that your display is outputting and compare the Delta E (a calculation of the amount of difference in color) from your original measured values. Your tolerance for Delta E difference will vary based on your industry and your needs, but we would usually recommend reprofiling if you have an average Delta E above 5.

Inkjet Printers

Modern inkjet printers generally are very consistent if used and maintained regularly. You should make sure you always use the same type and brand of ink and that the print heads stay free from clogs. Follow these rules for when to profile:

• You will need a separate profile for each combination printer, ink, paper and settings. Even two printers of the same make and model can print differently.
• Re-profile if you upgrade your operating system or change printer drivers.
• If  you begin to see a change in your printer's output, double-check your driver settings and test the print heads. If they are all fine, then re-profile.

Laser Printers

Laser printer present a challenge because their output can fluctuate dramatically based on temperature, humidity, paper type and volume of use. If your laser printer offers a calibration mechanism, be sure to use it frequently. In a high-volume or less environmentally controlled location, you may need to do this every few hours.

• Because of their variable nature, we recommend profiling often, for example each time toner is filled or replaced.

Scanners

Most scanners perform a self calibration periodically, often before every scan. This means they are usually very stable. Generally the only reasons why you would need to reprofile are:

• If you change scanner bulbs.
• Change scanner drivers.
• Notice an obvious change in the quality of your scans.