Datacolor User to User Support Group.

--- In colorvision_group@yahoogroups.com, "esimanor" <esimanor@...> wrote:

> Yes but how does one know how to relate between a setting in Candela 
> and the actual luminance level it will yield to the eye of the viewer? 
> Plus how do you take into account the level of ambiant light if what 
> you want is to achieve is respectively a given black and white point 
> luminance?
>

Thats a very good question.  The answer is you need to use a color
appearance model.  These models predict observed luminance and hue
based on multiple environmental factors.  One of the current
reasonably accurate color appearance models is given the name CIECAM02.  

First lets define two terms.  These terms are "Brightness" and
"Lightness".  As seen in "Color Appearance Models" by Mark Fairchild
these are defined as follows:
-------------------------------------------
Brightness
Attribute of a visual sensation according to which an area appears to
emit more or less light.

Lightness
The brightness of an area judged relative to the brightness of a
similarly illuminated area that appears to be white or highly
transmitting.

Note
Only related colors exhibit lightness.

The definitions of brightness and lightness are straightforward and
rather intuitive. The important distinction is that brightness refers
to the absolute level of the perception while lightness can be thought
of as relative brightness — normalized for changes in the illumination
and viewing conditions.
---------------------------------------------

One nasty twist of color vision is that using pure candela of a color
is insufficient to determine the relative lightness of two samples
given the same viewing conditions.

When you are asking about luminance level ... do you mean lightness or
brightness?

Tom