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PhotopigmentNomogramDemo

Compares photopigment nomograms against the CIE/Stockman-Sharpe tabulated
photopigment absorbance spectra (T_log10coneabsorbance_ss), which serve as
the fixed reference baseline. Each nomogram gets its own figure: thick black
lines show the CIE tabulated absorbance; the nomogram is overlaid in color.
Rows are L, M, S cones; left column is linear absorbance, right column is
log absorbance.

Lambda max values and nomogram comparison notes:

Each nomogram uses its own canonical lambda max values. Because the
nomograms have different shapes, they require different lambda max
parameters to approximate the same underlying spectrum.

For the L cone, the CIE absorbance peaks at ~551.9 nm (per the Fourier
polynomial fit of Stockman & Rider 2023, Table 1). The StockmanRider nomogram
reproduces this accurately at lambda max = 551.9 (zero shift). The
StockmanSharpe nomogram, which uses a polynomial approximation, requires
lambda max = 558.9 to best match the same CIE L-cone absorbance — a ~7 nm
discrepancy. This does not mean the two nomograms represent different spectra;
both target the same CIE L-cone, but StockmanSharpe is less accurate on a
linear scale (see note in StockmanSharpeNomogram.m). The visual difference
between the two curves reflects that accuracy difference.

For the S cone the discrepancy between nomograms is larger because
StockmanSharpe uses a single polynomial shape for all three cone types (just
shifted in log wavelength), while StockmanRider uses separately fitted Fourier
polynomials for L, M, and S. The CIE S-cone absorbance has a different shape
from L and M on a log-wavelength scale, so StockmanSharpe fits it less well.

The CarrollNeitz nomogram has a different history and was not developed
to match the CIE cone fundamentals. It provides a worse approximation to
to these, at least for the lambda max values we clocked in, which come
from a Netiz and Neitz review as referenced in the CarrollNeitzNomogram
function.

History:
2026-04-10 dhb Wrote it.
2026-04-10 dhb Restructured: CIE tabulated data as fixed black reference,
one figure per nomogram.