Matching colours in pictorial retouching: influence of the three colour dimensions and colour distortion phenomena

Our visual perception is strongly influenced by the anatomical structure of the eye and bylighting conditions. While looking at the painting, we perceive existing colour attributes,using retinal photoreceptors – cones – that serve our vision at higher luminance levels. Lighting, on the other hand, affects our colour discrimination as well as our perception ofthree dimensions of colour. During the retouching process our visual system can be affected by multiple optical impressionsthat many painting conservators are not fully aware of. Colour distortion phenomena canimpact our observation stealthily, while producing simultaneous contrasts and after images that interfere with our colour discrimination as well as our decisions in pigment mixing.The aim of this paper is to analyse these optical properties and to provide practical guidelines that will minimize colour distortion. One of the proposals is the use of 18% reflective grey card to cover adjacent colours around the paint loss. This method can be adopted as a helpful implement for tuning our colour perception.