Digital BW, The Print

I thought I would share a bunch of "bits and bobs" that I have learnt in the last few days.  
For what it's worth and in no particular order:

0.4 cd/m2 minimum luminance for a display such as my Apple LCD is directly transferable 
to the XYZ_Y value and hence equates to a L* value of 3.73 or a density of 2.38.  Like can 
be computed for the maximum luminance of a display (in my case 124 cd/m2).  And yes a 
display can have XYZ_Y values and L* values greater than a 100, being the value of 100% 
diffuse white.

The above information is stored in the ICC profile created by EyeOne for the display - see 
tags DevD and CIED.  Mac users can view these with Colorsync Utility.  (There are similar 
utilities for PCs.)  I don't know whether other calibration systems store the same 
information but if you want to know the emissive dynamic range of your display it may be 
worth checking.

D50 illumination standard is pervasive through ICC colour management.  It is regarded as 
average lighting for general home and office use comprising a mix of natural and synthetic 
lighting.  It is the reference lighting condition for the comparison of prints for the 
photography and graphic arts.  Hence it is embedded in our measurement devices.  
(People developing profiles to be used with perceptual or relative colormetric intents are 
obligated to provide the media white point data necessary to adjust for lighting conditions 
that are different from D50.)

It is interesting that the standard for measuring print reflectance data is for a black 
backing under the paper.  A lot of people, I believe, use white - including me.  This 
standard may change.