Datacolor Spyder3 Elite Help Manual page 29

follows:
Very Low: appropriate for prepress image editing. Calibrate the display to a White
Luminance level of 85-100 cd/m^2* and a White Point of 5000K (warm white) to
compensate for the eye's cooler response at low light levels. LCD monitors (including
laptops) can be used in this situation as well as CRT displays.
Moderately Low: dim, but appropriate for photo image editing. Calibrate the display
to a White Luminance level of 125-150 cd/m^2 and a White Point of 5800K (slightly
warm white) to compensate for the eye's slightly cooler response at moderately low
light levels. LCD monitors (including laptops) can be used in this situation as well as
very bright CRT displays.
Medium: appropriate for typical photo editing. Calibrate the display to a White
Luminance level of 175-200 cd/m^2 and a White Point of 6500K (medium white) to
compensate for the eye's moderate color response at medium light levels. Only LCD
monitors (including laptops) can be used in this situation.
High: uncontrolled, not recommended for color critical work. Lower the ambient light
if possible, otherwise use a monitor hood and calibrate the display to the maximum
White Luminance it can produce and a White Point of 6500K or higher.
Very High: uncontrolled, not recommended for any color managed work. If you must
work in these conditions use a monitor hood, umbrella or photographer's cloak and
calibrate the display to the maximum White Luminance it can produce and a White
Point of 6500K or higher.
CRT monitors should be used only at levels 1 and 2 since most large CRTs cannot
achieve a White Luminance over 125 cd/m^2. LCD monitors with limited White
Luminance should also be used only at levels 1 and 2.
Only LCD monitors should be used at level 3 and even then, some LCD monitors and
many laptops cannot achieve the 175 cd/cm^2 needed for good viewing in those
conditions.
If your monitor cannot achieve the recommended White Luminance level then you