radiometric {colorSpec}

convert a colorSpec object from actinometric to radiometric

Description

Convert a colorSpec object to have quantity that is radiometric (energy of photons) - to prepare it for colorimetric calculations. Test an object for whether it is radiometric.

Usage

## S3 method for class 'colorSpec'
radiometric( x, multiplier=1, warn=FALSE )

## S3 method for class 'colorSpec'
is.radiometric( x )

Arguments

x

a colorSpec object

multiplier

a scalar which is multiplied by the output, and intended for unit conversion

warn

if TRUE and a conversion actually takes place, the a WARN message is issued. This makes the user aware of the conversion, so units can be verified. This can be useful when radiometric() is called from another colorSpec function.

Details

If the quantity of x does not start with 'photons' then the quantity is not actinometric and so x is returned unchanged. Otherwise x is actinometric (photon-based).

If type(x) is 'light' then the most common actinometric unit of photon count is (\mumole of photons) = (6.02214 x 10^{17} photons). The conversion equation is:

E = Q * 10^{-6} * N_A * h * c / \lambda

where E is the energy of the photons, Q is the photon count, N_A is Avogadro's constant, h is Planck's constant, c is the speed of light, and \lambda is the wavelength in meters. The output energy unit is joule.
If the unit of Q is not (\mumole of photons), then the output should be scaled appropriately. For example, if the unit of photon count is exaphotons, then set multiplier=1/0.602214.

If the quantity(x) is 'photons->electrical', then the most common actinometric unit of responsivity to light is quantum efficiency (QE). The conversion equation is:

R_e = QE * \lambda * e / (h * c)

where R_e is the energy-based responsivity, QE is the quantum efficiency, and e is the charge of an electron (in C). The output responsivity unit is coulombs/joule (C/J) or amps/watt (A/W).
If the unit of x is not quantum efficiency, then multiplier should be set appropriately.

If the quantity(x) is 'photons->neural' or 'photons->action', the most common actinometric unit of photon count is (\mumole of photons) = (6.02214 x 10^{17} photons). The conversion equation is:

R_e = R_p * \lambda * 10^6 / ( N_A * h * c)

where R_e is the energy-based responsivity, R_p is the photon-based responsivity. This essentially the reciprocal of the first conversion equation.

The argument multiplier is applied to the right side of all the above conversion equations.

Value

radiometric() returns a colorSpec object with quantity that is radiometric (energy-based) and not actinometric (photon-based). If type(x) is a material type ('material' or 'responsivity.material') then x is returned unchanged.

If quantity(x) starts with 'energy', then is.radiometric() returns TRUE, and otherwise FALSE.

Note

To log the executed conversion equation, execute cs.options(loglevel='INFO').

Source

Wikipedia. Photon counting. https://en.wikipedia.org/wiki/Photon_counting

See Also

quantity, type, F96T12, cs.options, actinometric

Examples

sum( F96T12 )    # the step size is 1nm, from 300 to 900nm
# [1] 320.1132  photon irradiance, (micromoles of photons)*m^{-2}*sec^{-1}

sum( radiometric(F96T12) )
# [1] 68.91819  irradiance, watts*m^{-2}