>Psychtoolbox>PsychColorimetric

[absorbanceSpectra, absorbanceSpectraWls] =…
AbsorptanceToAbsorbance(absorptanceSpectra, absorptanceSpectraWls, axialOpticalDensities, [NORMALIZE])

This code inverts AbsorbanceToAbsorptance. You might want to do this if you were trying
to take cone fundamentals and back down all the way to the component parts, so that you
could for example vary the axial density and recompute the fundamentals.

The absorbance/absorptance terminology is described at the
CVRL web page, http://cvrl.ucl.ac.uk. Wyszecki and Stiles refere to absorbance
the absorption coefficient (p. 588).

Both absorptance spectra and absorbance spectra describe quantal absorption.

Absorbance spectra are normalized to a peak value of 1.
Absorptance spectra are the proportion of quanta actually absorbed.

Equation: absorptanceSpectra = 1 - 10.^(-OD * absorbanceSpectra)

Multiple spectra may be passed in the rows of absorbanceSpectra. If
so, then the same number of densities should be passed in the vector
axialOpticalDensities, and multiple answers are returned in the rows
of absorptanceSpectra.

NORMALIZE (default true) causes this routine to normalize the returned absorbances to
have a maximum of 1.

Note, we now have ways of building up most fundamentals that we care about
from constituant parts, and thus probably don’t need to do that. See
CIEConeConeFundamentlsTest, ComputeCIEConeFundamentals, DefaultPhotoreceptors, FillInPhotoreceptors,
IsomerizationsInEyeDemo.

Originally written by HH, Copyright HH, Vista Lab, 2010

8/11/13 dhb Moved into PTB, modified comments so as not to refer to non-PTB routines.
dhb That this actually inverts is tested in IsomerizationsInEyeDemo.
12/02/13 dhb Fix spelling of “absorptance” in routine names and throughout.