Re: Luminance nomenclature, STILL wanting to see constant L*
Re: Luminance nomenclature, STILL wanting to see constant L*
- Subject: Re: Luminance nomenclature, STILL wanting to see constant L*
- From: Roger Breton <email@hidden>
- Date: Sat, 11 Nov 2006 23:34:05 -0500
> Roger gives the correct integrated definition of Luminance. The CIE
> gives the functional/working definition of Luminance with the
> Luminosity Function. The CIE defined the Luminosity Function in order
> to relate perceived brightness to radiated energy. They defined the
> tristimulus value Y (of XYZ) to match the Luminosity Function. The
> "L*" of CIELAB is another representation of Luminance, and is the one
> probably most relevant to this list.
>
> Hope that clears things up. See you at the Color Imaging Conference!
> John
Hi John,
Looks like we missed each other at the conference!
Anyhow, just want to bring to your attention that you abuse the word
Luminosity, IMHO. Unless I completely missed this, but, to my knowledge,
there is no such thing as a "Luminosity" function. There is a "Visibility"
function. That's where the capital V comes from, in V-lambda. I'm looking at
CIE Publication 15.2, on page 3, and I see the expression "photopic luminous
efficiency function" but nowhere "luminosity". A quick search on Google with
"Luminosity function" returns plenty of hits dealing with stars and
astronomy but nothing in terms of the Standard Photopic Observer.
Otherwise your account of the Visibility Function is correct.
If you can supply some kind of reference or URL, I'd be curious to look it
up. I may be wrong.
Regards,
Roger Breton | Laval, Canada | email@hidden
http://pages.infinit.net/graxx
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