The ‘Intuitive Overlays’ were developed by Professor Arnold Wilkins of the Visual Perception Unit at Essex University. They have been manufactured by a specialist printer to the highest quality control standards. They are also the only overlays the design and use of which have been described in a quality optometric journal (Ophthal. Physiol. Opt., 1994).

The complete range of colours that we can perceive is described on the CIE u ‘v’ map of colour space. This resembles a triangle, with white being placed near the centre and blue, red, and green at each of the apices. The overlays have been scientifically designed to sample this colour space systematically.

Each of the nine colours is equidistant from white. This means that they have equivalent saturations.

Nine colours have been chosen so that the separation between adjacent colours is similar. The overlays can be combined by superimposing one upon another to obtain a very large range of resultant colours.

The intuitive overlays are scientifically designed, based on human colour space. Spectral reflectance curves are approximate