Talk:Optical density

Other uses

'Optical density' is sometimes also used to describe a material's refractive index, for example in Bose-Einstein condensate, Speed of light, [1], [2]. R6144 08:16, 23 August 2005 (UTC)

I have high-school text books (Merrill, Glencoe) that also use optical density and refractive index interchangeably. Ronstew (talk) 20:48, 2 July 2008 (UTC)

Where is this definition from?

According to the source http://www.its.bldrdoc.gov/projects/devglossary/ which is cited in this article, optical density is log(1/T), and not log(1/T)/pathlength. Therefore, it would be synonymous with absorbance which is noted at the bottom of the article. I couldn't find the definition listed in the other source. It seems logical to have a distinction between the OD and A, and the term density implies a per length unit, but the problem is that I can't find a source anywhere to back this up.

Justin thats not true!!!!!!!

AFAIK, optical density was originally defined by Hurter and Driffield as D = log10(O) to indicate the amount of an opaque substance suspended in a transparent medium:

"For our purposes, i.e., in its application to negatives, the density is directly proportional to the amount of silver deposited per unit area, and may be used as a measure of that amount ... The density is the logarithm of the opacity, or the negative logarithm of the transparency ... The reason why we prefer to have the results expressed as density is because the density is a measure of the amount of silver deposited, or of the chemical work done by the light." (Hurter & Driffield, "Photo-chemical Investigations and a New Method of Determining the Sensistiveness of Photographic Plates.", The Journal of the Society of Chemical Industry 1890. No.5, Vol.IX. Reprinted in The Photographic Researches of Ferdinand Hurter & Vero C. Driffield 1920 pp.78-79)

--Redbobblehat (talk) 16:36, 6 March 2009 (UTC)