Datacolor User to User Support Group.

I appreciate you taking the time to explain it to me and I really want
to get this right.

Assumptions:

1) Bulb contribution

5000K rated bulbs determine the color temperature of emitted white
light regardless of its intensity.

These bulbs are useful in the context of examining prints calibrated
for white at 5000K.

2) Illumination contribution

Illumination relates to the intensity and distance of a light source.

Relative illumination (light intensity in candelas / meter^2) measured
at the monitor represents illumination minus distance loss.

I can measure this (in candelas / meter^2) using the provided colorimeter.

If the colorimeter is pointed at the monitor, I am measuring the
monitor contribution whereas if it is pointed away from the monitor I
am measuring the contribution of the light source.

Both sources of light contribute to the overall illumination affecting
the eyes.

Rods (B&W vision) are more sensitive to low illumination whereas cones
(color vision) require more illumination.

To properly assess color one needs enough illumination so that eyes
use mostly cones.

With high levels of ambient light one should select higher temperature
monitor targets where as in low levels of ambient light one should
select lower temperature monitor targets.

Questions:

Assuming the colorimeter is pointed away from the monitor how much
illumination is required i.e. what would be a good interval measured
in candelas / meter^2 for vision to mostly use cones?

Given measure X candelas / meter^2 within this interval a monitor
target of 5000K should be used, right?

For some reason I am being very "dense" about this but I am trying to
ensure I properly setup my environment to make the most of my color
vision purchase.

Thanks,
Pierre


--- In colorvision_group@yahoogroups.com, CDTobie@... wrote: 
> Candelas per meter square IS the monitor target value; which is
related to 
> suggested ambient light levels (or ambient light levels are related
to suggested 
> target monitor values, you can adjust either).
> 
> Using 5000k lights and calibrating to 5000k will not solve the
issue: lots of 
> 5000k ambient light would still require a monitor temperature of
6500k, since 
> it would stimulate the rods less and the cones. A tiny amount of 6500k 
> ambient light would require you calibrate the monitor to 5000k. Do
you begin to see 
> that monitor temperature and ambient light temperature are unrelated
items? 
> The eye is variable in how it perceives color, so the monitor must
be adjusted 
> for that, not the color of that light.
> 
> C. David Tobie
> Product Technology Manager
> ColorVision Business Division
> DataColor Inc.
> CDTobie@...
> www.colorvision.com
>