chemistry of artists' materials

additive colour mixing

1. source is observed directly

2. primary colours are red, green, blue

3. mix to make white light

4. method through which emitted light mixes 

5. e.g. screens, light

subtractice colour mixing

1. observed via reflection or transmission

2. primary colours are magenta, cyan and yellow

3. mix to make black

4. e.g. pigment, dye, paint mixing

rods

1. monochromatic (scotopic vision)

2. active in low illumination conditions

3. only one kind

4. contains rhodopsin which photobleaches under high illumination conditions

cones

1. colourful (photopic) vision

2. active in high illumination conditions

3. come in short, medium and long peak sensitivities which perceive blue-violet, green and red-orange respectively

4. contains iodopsin

colour at 400-435nm

violet

colour at 435-480nm

blueco

colour at 480-500nm

green-blue and blue-green

colour at 500-560nm

green

colour at 560-580nm

yellow-green

colour at 580-595nm

yellow

colour at 595-605nm

orange

colour at 605-750nm

red

five groups of the causes of colour

simple excitations, ligand field effects, molecular orbitals, band theory, geometrical and physical optics 

colour can be defined through which three attributes

hue, strength/intensity, brightness

how is hue measured

the values of absorbed wavelengths of light

how is strength/intensity measured

magnitude of molar extinction coefficient at maximally absorbed wavelength

how is brightness measured

the narowness of the absorption band

monochromatic light

light of a single, defined wavelength with a narrow linewidth (a few nm wide)

nonspectral colours

colours which cannot be produced by monochromatic light (eg pinks and purples which require triggering of multiple cones)

continuous light

light which contains all the wavelengths (white light, the sun)