The role of delineation and spatial frequency in the perception of the colours of the spectrum

The observations of the spectrum made by Newton, Young, Wollaston and Helmholte are approximated and accounted for. Increasing the number of delineations allows progressively more bands differing in colour to be perceived, in addition to the three blocks of colour seen in the undelineated spectrum. The rate at which further delineation permits more colours to be observed decreases, however, so that up to 30 colours can be perceived in the subdivided spectrum. The wavelength discrimination measurements agree well with previous data. Enhanced colour discrimination is shown to require luminance contrast transients containing only the first few Fourier harmonics.