I assumed Mark was wanting a light source of a known luminance, to check
the numbers output by his photometer. I don't have any knowledge to
offer, but I get my photometer calibrated at Optical Test and
Calibration Ltd, http://www.otc.co.uk/, and assume they or a similar
company would be able to provide more information if you were to
approach them...
Best wishes,
Jenny
Nils T Siebel wrote:
> 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
>>
>>
>>
>> _______________________________________________
>> visionlist mailing list
>> visionlist at visionscience.com
>> http://visionscience.com/mailman/listinfo/visionlist
>>
>>
>>
>
>
>
>
--
Dr Jenny Read Office: +44 191 222 7559
Royal Society University Research Fellow Mobile: +44 794 401 5796
Institute of Neuroscience, Fax: +44 191 222 5227
Faculty of Medical Sciences, mailto:J.C.A.Read at ncl.ac.uk
Newcastle upon Tyne, NE2 4HH, UK. http://www.staff.ncl.ac.uk/j.c.a.read