• ‘Light Reflectance Value’ (LRV) is the total quantity of visible light reflected by a surface at all wavelengths and directions when illuminated by a light source.

• ‘Visual Contrast’ is the perception of a difference visually between one element of a building and another by reference to their LRV’s

• Differences in LRV should be used to assess the degree of Visual Contrast between surfaces such as floors, walls, doors and ceilings and between key fittings/fixtures and surrounding surfaces.

"For people with adequate vision, differences in hue (the nature of the colour) or chroma (the intensity of the colour) will provide adequate visual contrast. Unfortunately, this is not so for all people who are visually impaired. The main feature of a surface, which appears to be strongly correlated with the ability of blind & partially sighted people to identify differences in colour, is the amount of light the surface reflects, or its Light Reflectance Value (LRV)."

"The LRV scale runs from 0, which is a perfectly absorbing surface that could be assumed to be totally black, up to 100, which is a perfectly reflective surface that could be considered to be the perfect white. Because of practical influences in any application, black is always greater than 0 and white never equals 100."

"The evidence-based research available to date allows a degree of variability concerning the minimum LRV difference that is required to provide adequate visual contrast for blind & partially sighted people. Whilst there is considerable confidence in recommending a difference in LRV of 30 points or more, there is also some evidence to suggest that a difference of around 20 points might still be acceptable provided the illuminance on the surfaces is 200 lux or more. Differences less than about 20 points might not give adequate contrast, even with an illuminance of 200 lux on the surfaces. In the case of door opening furniture, the ease with which blind and partially sighted people are able to distinguish furniture against its background is influenced by its 3D form giving light and shade and the shiny nature of the finish, whether metallic or non-metallic. For such products, it is considered that a difference in LRV between the product and its background of at least 15 points is acceptable."

"It is thought that LRV differences are less important between two large areas, e.g. between wall and floor, than between a small object on a larger background surface, e.g. a lever handle on a door."