Dartnall's rhodopsin template or nomogram

Data key


  1. 1/λ - 1/λmax
  2. Log relative absorbance

where 1/λ is the wavenumber, and 1/λmax is the wavenumber of maximum sensitivity of the photopigment, both in cm-1.


From Table 1(8.2.3) of Wyszecki & Stiles (1982).

    The template reflects Dartnall's hypothesis that pigment shapes are invariant when plotted on a wavenumber scale (Dartnall, 1953). The shape of any pigment can then, in principle, be calculated from Dartnall's nomogram simply by adding the pigment's wavenumber of maximum sensitivity to each value.

    More recently, it has been shown that pigment shape invariance is improved when other scales, such the fourth root of wavelength (Barlow, 1982) or log frequency (Mansfield, 1985), are used. Thus, the Dartnall nomogram remains useful, but over only a restricted range of wavenumbers near the rhodopsin λmax.


Barlow, H. B. (1982). What causes trichromacy? A theoretical analysis using comb-filter spectra. Vision Research, 22, 635-643.

Dartnall, H. J. A. (1953). The interpretation of spectral sensitivity curves. British Medical Bulletin. 9, 24-30.

Mansfield, R. J. W. (1985). Primate photopigments and cone mechanisms. In A. Fein, & J. S. Levine (Ed.), The visual system New York: Alan R. Liss.

Wyszecki, G., & Stiles, W. S. (1982). Color Science (2nd ed.). New York: Wiley.