Pastel colours
Perceptibility
Perfect reflecting diffuser
See diffuser.
Perfect transmitting diffuser
Phosphorescence
Photochromism
A reversible change in colour of a specimen due to exposure to light (or other radiant flux) without appreciable heating of the specimen.
Photoluminescence
Luminescence produced by the absorption of radiant flux. Destinguished from ordinary reflection by a time delay and usually, an upward shift in wavelength.
Photometer
Photophobia
Photopic vision
Pigment
A non-soluble colorant as opposed to a dye which is soluble.
Pineo correction
An empirically determined correction (for textiles) applied to the measured reflectance to improve the linearity between colorant concentration and K/S. The formula is as follows:
It is mainly the dark and stronger (more saturated) colours that are affected by this correction. Also see Saunderson correction for paints and plastics,
Pitt's primaries
Planck radiation law
Planckian locus
Planckian radiator
Polarisation of light
Primaries
Primaries (CIE)
Protanomalous vision
Protanopia
Pure colour
Purity
Purkinje effect