Eric Perlberg , Aug 24, 2005; 05:33 a.m.
According to Bruce Fraser (a recognised authority on colour management), the standards that you're talking about are designed for the graphic arts. I'm not sure about ISO 12646 but ISO 3664 calls for 500 lux for practical appraisal and 2000 lux for critical comparison. If the same holds true for 12646 as 3664 Fraser has this to say:
"...the standard wasn't created with monitor to print matching in mind- it mandates that the ambient illumination for color monitors should be less than or equal to 32 lux and must be less than or equal to 64 lux. For monitor to print matching, all these values are way too high- the ISO has acknowledged this and is still working on standards for this kind of match" (pg 210, Real World Color Management, ISBN 0-201-77340-6) Book is highly recommended.
Most color management experts that I've read set their LCDs to the following: 1) around 100 cd/m2 depending on ambient light 2) Gamma 2.2 (yes even for apple, the native gamma of the apple lcd range is 2.2 not 1.8) 3) Color temp at 6500k
From what I've read, the best technique to compare on screen images to your light box is to try to balance the light box illumination to roughly that of your screen and when looking between the monitor and paper print, either close your eyes for a second or look at some neutral coloured wall.
The reason is that a) 5000k on a monitor makes everything look a bit yellow and most people find 6500k a more natural monitor temp and b) your eye/brain quickly adjusts its sense of white balance to compensate for the difference in colour temp dif between the monitor and light box.