Light reflectance value – Grey areas give out more information than striking colours


Ian Streets of About Access discusses the impact of colours, light reflectance value and its impact on construction.

The 2017 FA Cup Final was one to remember. It was an action-packed game with flashes of controversy and victory for the underdog as Arsenal in their red shirts overcame the blues of Chelsea.

Rewind to any year before the first technicolour final in 1968 and things would have looked very different, with both sides rendered grey in the days of black and white TV. But that’s how some people will have viewed this year’s showpiece, with the tone of the players’ shirts more important than the colour for some people with a visual impairment.

Back in the 60s, as now, the way round the problem was a change of shirts. In 1963 Leicester City wore white instead of their traditional blue for their final against the reds of Manchester United, in the same way that one side would have had to change if United had progressed to meet Arsenal this season.

Cricket has shown awareness of the issues by using a white ball and black sight screens for night matches. Snooker was, well… snookered at times when it came to differentiating between red and blue or brown and green on a black and white TV screen. But it took off from 1969 with the launch of Pot Black making the most of colour TV.

To get an idea of the difficulties just tinker with the brightness controls on the TV, or take a look online at some old black and white images of sport. And then apply what you see to everyday life in the 21st century.

For people who do not have a visual impairment, setting a red door in a blue wall would not present a problem, but people who are partially-sighted rely on tonal contrast for information. In making their way around a building, they need certain things to stand out from their background.

Light reflectance value

The key factor is the light reflectance value of a colour, and that is measured on a scale from zero to 100. Zero is perfectly absorbing, such as black. A hundred is perfectly reflecting, such as white. It is impossible to achieve either extreme, and the range you should aim for depends on lighting levels and the scenario.

A floor in a building would typically be rather darker than the walls, so closer to zero. Walls will therefore be closer to 100.

With other features in a building the difference is usually more subtle, and the requirements are influenced by lighting levels. What the designers should try to achieve is two colours that give 30 points of difference if lighting is 200 lux or less. If lighting is more than 200 lux then 20 points difference is considered acceptable, but it can change depending on the facilities and the location.

With signage, if you really want to get the message across then it is recommended that the difference between the text and the background is 70 points.

Door furniture is recommended to have 15 points difference between the handle and the immediate background, with the additional factor in this scenario being that the 3D shape creates a shadow.

Stair nosings depend on the lighting in the area, but you would normally expect 30 points difference. Hand rails to stairs, support rails in an accessible WC, doors and adjoining surfaces all need to be considered in the same way.

The important thing to remember is that striking colours might not appear that different to people who are visually impaired. But if you have two colours that have a contrast in tone rather than in hue, such as a light grey and a dark grey, most people who have a sight impairment, as well as those who do not, will be able to tell the difference.


Case study

We recently undertook an accessibility audit of a dental practice and identified a potential problem for visually-impaired people in using the stairs. There were no issues with the steps themselves but the handrails and the wall to which they were fixed were both bright white. This could make it difficult for some people to see the rail clearly.

By using tonal contrast any problems can be avoided, and this is particularly important when designing accessible WCs. Such facilities as support rails and sanitary ware can be difficult to identify if they are white and fixed to a white background.


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