[visionlist] Reference Source

[Nils T Siebel]

Dear Mark,

If you are looking for a reference for the definition of "luminance"
and other terms in video/TV technology the CIE recommendations (e.g.
601, 709)  are the definitive sources.  In a more practical sense the
following text is a very good source of information, with formulas
etc. (the CIE recommendations are also cited and explained there):

@Misc{FordRobe98,
  author =       {Adrian Ford and Alan Roberts},
  title =        {Colour Space Conversions},
  howpublished = {Available at \url{http://www.poynton.com/PDFs/coloureq.pdf}},
  month =        {August},
  year =         1998
}

Charles Poynton's colour home page at
http://www.poynton.com/Poynton-color.html is a good starting point for
more information.  His colour FAQ is a very good source, too.

>From the colour FAQ:

"3. What is luminance?

"Brightness is defined by the CIE as the attribute of a visual
sensation according to which an area appears to emit more or less
light. Because brightness perception is very complex, the CIE defined
a more tractable quantity luminance which is radiant power weighted by
a spectral sensitivity function that is characteristic of vision. The
luminous efficiency of the Standard Observer is defined numerically,
is everywhere positive, and peaks at about 555  nm. When an SPD is
integrated using this curve as a weighting function, the result is CIE
luminance, denoted  Y.

"The magnitude of luminance is proportional to physical power. In that
sense it is like intensity. But the spectral composition of luminance
is related to the brightness sensitivity of human vision.

"Strictly speaking, luminance should be expressed in a unit such as
candelas per meter squared, but in practice it is often normalized to
1 or 100 units with respect to the luminance of a specified or implied
white reference. For example, a studio broadcast monitor has a white
reference whose luminance is about 100  cd*m -2, and Y  =  1 refers to
this value."

Hope this helps,

Nils.

On Wed, Apr 9, 2008 at 9:25 PM, Dr. Mark Brady <mark.brady at ndsu.edu> wrote:
>
>  Dear Colleagues,
>
>  Does anyone have any suggestions for a luminance reference source for use
> in calibrating photometers?
>
>  Mark J. Brady
>
>  Department of Psychology
>  North Dakota State University
>
>
>
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>



-- 

Nils T Siebel
Cognitive Systems Group
Institute of Computer Science
Christian-Albrechts-University of Kiel
Olshausenstr. 40
24098 Kiel, Germany.