LRV is a universal value for 'contrast'. It measures the proportion of useful light reflected by a coloured object. It represents a relative light and darkness value rather than an actual colour. Therefore, dissimilar colours could have the same LRV.
LRV is measured on a scale of 0 to 100, 0 being perfect absorbing black and 100 being perfect reflecting white (in reality you never find these perfect objects - a bright white would typically have a result of an LRV of 85).
Most registered blind people will still have some vision in colour. Only a small percentage (less than 5%) can see nothing at all, and even people within this group will generally have some sensitivity to light and shade. Ensuring that a minimum of 30 points of LRV difference is specified for adjacent surfaces will in the majority of cases help to ensure that visually impaired people are not discriminated against.
Examples where visual contrast will be required:
• Door faces and/or frames to walls
• Floors to walls