The SLL Lighting Handbook by Peter Boyce , Peter Raynham

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The motors of a steel rolling mill, local fluctuations in supply voltage are likely and, in consequence, so are fluctuations in light output of incandescent light sources. These can be minimised by using a voltage regulator between the electricity supply and the light source. Discharge lamps are less sensitive to supply voltage fluctuations than incandescent lamps because the electricity supply is filtered through the control gear. Electromagnetic control gear typically produces an output at the same frequency as the electricity supply.

All the rod photoreceptors are the same, containing the same photopigment and hence having the same spectral sensitivity. 5. The other three photoreceptor types are all cones, each with a different photopigment. 6 shows the relative spectral sensitivity functions of the three cone photoreceptor types, called short (S), medium (M) and long (L) wavelength cones. 7). Cones are concentrated in one small area that lies on the visual axis of the eye, called the fovea, although there is a low density of cones across the rest of the retina.

E. colours that lie along the vertical value axis and hence have no hue or chroma, are coded as Neutral 1, Neutral 2 etc. depending on their reflectance. To a first approximation, the percentage reflectance of a surface is given by the product of V and (V–1) of the surface, where V is the Munsell value of the surface. 10 The organisation of the Munsell colour order system. The hue letters are B = blue, PB = purple/blue, P = purple, RP = red/purple, R = red, YR = yellow/red, Y = yellow, GY = green/yellow, G = green, BG = blue/green.