Determination luminance value/brightness

Pet Peeve concerning the misuse of the term Luminance (which has been in Photoshop and other applications for years but doesn’t make it a correct term). 

Luminosity is a measure of the total radiant energy from a body. It has nothing to do with what a human observer perceives but rather describes the total radiant energy, such as watts/second of a source (the surface of a radiating object like a display). In Photoshop, the layer mode called luminosity is not what's happening here (I was told its something like the "Luma" which is an old TV RGB transform)

Lightness is a perceptually scaled component of color, the axis seen in Lab (Lstar) from light to dark. It IS the L in HSL. 

Surely, effective luminance is mainly a product of the device showing an image. If a display screen has a higher "white  luminance" then the whole image will increase in luminance. Colours in an image do, of course, have an Lab value (L being luminance.) for each pixel.

I hope this helps
neil barstow, colourmanagement net :: adobe forum volunteer
google me "neil barstow colourmanagement" for lots of free articles on colour management
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The perfect program for this is Mathematica.  In that program you can even run your eyertacking simulations and find different contrast areas other than simple luminance.  The advantage to using Mathematica is it's amazing graphing functions.  Here are some examples to get you started.  

A picture has millions of luminance values, not one. Ditto videos.