Units |
0.1 nm steps |
1 nm steps |
5 nm steps |

Quantal (log) |
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Energy (log) |
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Energy (linear) |

**Columns**

*Quantal*

Logarithmic

- Wavelength (nm)
- log 2-deg photopic luminous efficiency,
*V*_{2}**(**l**)*

*Energy*

Logarithmic

- Wavelength (nm)
- log 2-deg photopic luminous efficiency,
*V*_{2e}**(**l**)*

Linear

- Wavelength (nm)
- 2-deg photopic luminous efficiency,
*V*_{2e}**(**l**)*

Based on
the linear combination of the Stockman and Sharpe
(2000) M- and L-cone spectral sensitivities that best fits
experimentally-determined 25-Hz, 2° diameter, heterochromatic (minimum)
flicker photometric data obtained from 40 observers (35 males, 5 females) of
known genotype, 22 with the serine variant L(ser180), 16 with the alanine
L(ala180) variant and 2 with both variants of the L-cone photopigment. The
matches, from 425 to 675 nm in 5-nm steps, were made on a 3 log troland xenon
white (correlated color temperature of 5586 K, but tritanopically metameric with CIE
D_{65} standard daylight for the Stockman & Sharpe (2000) L- and
M-cone fundamentals) adapting field of 16° angular subtense,
relative to a 560 nm standard. Both the reference standard and test lights were
kept near flicker threshold so that, in the region of the targets, the total
retinal illuminance averaged 3.19 log trolands. The new function is
extrapolated to wavelengths shorter than 425 nm and longer than 675 nm using
the Stockman & Sharpe (2000) cone fundamentals. The quantal luminous
efficiency function is:

or

relative to the quantal
cone fundamentals and having unity peak sensitivities. Functions are
tabulated at 0.1, 1 or 5 nm steps. The 0.1 and 1 nm functions were
obtained by the interpolation of the 5 nm functions using a cubic spline. Functions are normalized to peak at unity at
the nearest 0.1 nm step. The l_{max} for
quantal efficiencies is 545.6 nm.

The *same function*, but energy based, and
given in terms of the *energy based*
cone fundamentals and renormalized to unity peak sensitivities:

or

The
different weight simply reflects the unity renormalization required after the
cone fundamentals are converted from quanta to energy units. The l_{max} for energy-based efficiencies is 555.5 nm.

**NB** This is a update of the preliminary estimate of *V _{2}**(l), given previously in Stockman & Sharpe (2000) and previously
tabulated here. The preliminary estimate, which had an L-cone weight of
1.50, was based on the first 22 of the
40 observers used to obtain the final estimate.

Stockman, A., & Sharpe,
L. T. (2000). Spectral sensitivities of the middle- and long-wavelength
sensitive cones derived from measurements in observers of known genotype. *Vision
Research*,* 40,* 1711-1737.

Sharpe, L. T., Stockman,
A., Jagla, W. & Jägle,
H.(2005). A luminous
efficiency function, *V**(l), for daylight adaptation. *Journal of Vision, 5, 948-968*.