Qr {colourvision}

Photoreceptor relative quantum catch

Description

von Kries transformation. Photoreceptors are assumed to be adapted to the background. This function is used internally in colour vision models.

Usage

Qr(R, I, Rb, C, interpolate, nm)

Arguments

R

Reflectance of observed object. A data frame with two columns only: first column corresponding to wavelength values and second column with reflectance values.

I

Irradiance spectrum. A data frame with two columns only: first column corresponding to wavelength values and second column with irradiance values. Irradiance values must be in quantum flux units.

Rb

Background reflectance. A data frame with two columns only: first column corresponding to wavelength values and second column with reflectance values. Photoreceptors are assumed to be adapted to the background reflectance.

C

Photoreceptor sensitivity curve. A data frame with two columns only: first column corresponding to wavelength values and second column with photoreceptor absorbance values.

interpolate

Whether data files should be interpolated before further calculations. See approx.

nm

A sequence of numeric values specifying where interpolation is to take place. See approx.

Details

For the von Kries transformation, first the quantum catches of the observed reflectance and the environmental background are calculated (see Q). Then:

qi = \frac{Q_i}{Q_{bi}}

where Q_i is the quantum catch arising from the observed object and Q_{bi} is the quantum catch from the background, for each one of the photoreceptor types (i).

Value

Photoreceptor relative quantum catch.

Author(s)

Felipe M. Gawryszewski [e-mail]

References

Backhaus, W. 1991. Color opponent coding in the visual system of the honeybee. Vision Res 31:1381-1397.

Chittka, L. 1992. The colour hexagon: a chromaticity diagram based on photoreceptor excitations as a generalized representation of colour opponency. J Comp Physiol A 170:533-543.

Endler, J. A., and P. Mielke. 2005. Comparing entire colour patterns as birds see them. Biol J Linn Soc 86:405-431.

Vorobyev, M., and D. Osorio. 1998. Receptor noise as a determinant of colour thresholds. Proceedings of the Royal Society B 265:351-358.

See Also

CTTKmodel, EMmodel, RNLmodel, RNLthres, GENmodel