Acceptable Light Damage - A Preliminary Investigation

An attempt is made to relate the degree of colour change in works of art, oil paintings and watercolours in this instance, to a subjective assessment of how acceptable these changes are over a given length of time. A panel of observers was presented with pairs of reproductions of figurative and abstract oil and watercolour paintings, regions of which had been altered digitally prior to printing to give a known colour difference from the original. In the first part of the study, the observers were asked if a colour difference could be observed, to assess the scale of a Just noticeable difference' (JND) in these complex scenes. In the second part, observers assessed the acceptability of a change over a period of 10, 50 or 100 years. The results demonstrated that the JND is sometimes larger in complex scenes than in simple colour pairs and that changes in smaller areas, more peripheral areas, or areas in abstract images are less noticeable. In the second phase of the study, changes to the figurative oil painting were generally deemed less acceptable than changes of equivalent magnitude in the abstract or watercolour images. The implications of the findings for museum lighting policy and the concept of a (serviceable life'for objects are explored.