i literally regurgitated a lesson from my physics class, so if what i said is wrong, it wouldnt suprise me. it wouldnt be the first time we learned about something that didnt happen.
everyone here seems to agree though that pure white and pure black are at the very least constantly percieved, which is good enough for me. Even with the most extereme possible aperature/iris diameters, theres such a breoad range of light that is either too much or too little to get our eye's attention, isnt art all about how things are seen, anyway? unless you are a hyperrealist and want to make things more detailed (and therefor, imo, much less interesting) than they acutally are.
Helm might be on the right track here i think.
art black and art white - these should be used in moderation to draw sharp attention. oftentimes they will be percieved as ugly or garish because of the contrast, so in cases they should not be used. as pigments, they drain chroma from a mixture, and therefore should only be mixed with paints that are already as dark as they will get by mixing "pure" colors, or as light, if the artist wishes to maintain any vibrance in their work. If vibrance is not an issue, go ahead and use them.
on my palettes i almost never use black unless i am imitating a style. the hercules picture i posted in the OT creativity thread uses black because it is vaguely immitating the style of 16th century dutch painters. i also tend not to use white as a paint, relying instead on the white of the canvas, but sometimes, if i need to paint with light colors, particularly over dark ones, i will add white.
in monchromatic or achromatic works, value contrast is your closest friend. make sure you use the darkest darks and the lightest brights available to you so that you can maximize your range of values.
