optical density

dbk at aberystwyth.ac.uk dbk at aberystwyth.ac.uk
Tue Apr 2 06:08:06 EST 1991

OD and Absorbance are *NOT* the same. Absorbance refers to the absorption
of light *BY A CHROMOPHORE*. OD refers to the amount of light that sets
out from the source but doesn't reach the detecctor. In biology, the usual
reason is that it is *SCATTERED* (mainly elastically), not that it is
absorbed. Hence the difference in terminology. As Michael Caine might say,
"not many people know this".

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