Mean data from Table 1 of Kraft, Schneeweis & Schnapf (1993). n, the number of records averaged together, varies from 1 to 12 depending on wavelength.
Suction electrode (current) recordings made with a light beam passing transversely through human rod outer segments.
The λmax value is ~495 nm.
Kraft, T. W., Schneeweis, D. M., & Schnapf, J. L. (1993). Visual transduction in human rod photoreceptors. Journal of Physiology, 464, 747-765.