Luminance Contrast: How to measure it?

Grey steps with no contrast nosing blends into the grey paving.
Grey steps leading to a grey footpath.

Visual contrast, or luminance contrast, is a key feature of universal design, but how well can we measure it? It’s a mainstream issue and something designers need to consider from the outset. It’s one thing to know the importance of visual contrast, but knowing how to measure it is another.

The glare from the doorway backlights the sign to the toilets which is mounted near the ceiling and hard to see.
Backlight makes toilet sign hard to see

For most people, vision is their most dominant sense. About 80% of our perception, learning, cognition and activities use visual cues. Contrast helps us detect objects from the background and to perceive distance.

Inadequate contrast leads to confusion and difficulty negotiating the environment, even if only temporarily.  Australian Standards require a certain level of luminance contrast in the built environment. But most access consultants use their own eyes as the measuring tool. Is this good enough? Probably not.

A shopping mall with a shiny floor reflecting rows of lights from the ceiling. It looks very confusing.
A photo shows the confusing visual cues

Penny took delegates through the two main measuring instruments and there is good reason for not using them. One is costly and the other is heavy and bulky. Then she introduced a free app for a smart phone called Get Luminance. While there is still more work to do on establishing the validity of the app, it gives a better guide than a guess by eyesight.

There is much to consider in Penny’s presentation and paper and it is good to see that there is a solution. Photographs are two dimensional and often provide an indication of poor contrast. If the place is unfamiliar it is sometimes difficult to make out certain features. For example, a stainless steel sign against a concrete wall. 

Penny wrote an article with Richard Bowman, Luminance Contrast Standards, the Boy Who Could, and Visionary Pathfinders. The article discusses the inadequacy of standards in reflecting user experience. 

Norwegian study on staircases

Grand staircase in a heritage building showing a blue carpeted staircase and a mural at the top of the flight. As our populations age we will have more people experiencing low vision. This means that contrasts between objects will become an increasingly important factor in negotiating the built environment.

Although standards stipulate a certain luminance contrast and levels of light (lux) for buildings, how are they measured, who measures them, and what are they measured with?

This issue was investigated by a team in Norway using staircases for the case studies. They found that the tools used by builders and planners vary, and this results in different contrast and light readings for the same staircase. Other variables were also found to influence the readings, such as reflection or glare from overhead lighting. Sunny or cloudy conditions, the shadow of the measurer when measuring, and different angles and positions of the meter all bring different results.

stairs-red-and-blue-1611679__180The findings and conclusion of the study raise an important question: Are the staircases as bad as they seem in terms of not meeting the legislative requirements? Or are the requirements too difficult to fulfil? The team concluded that the answer lies with a representative group of people with low vision guiding them on understanding usability. Another case of standards being useful but not entirely effective – the users have the answer once again.

The article, Planning and Measuring Luminance Contrast in Staircases contains charts, graphs and pictures that illustrate their methods and results. The article is free to download.

L.D. Houck1 , K. Gundersen, O. Strengen: Universal Design 2016: Learning from the Past, Designing for the Future. H. Petrie et al. (Eds.)

Seeing the Light

Photo showing visual distortion and reflections in a glass doorWhat is luminance contrast and how do you measure it? The non-technical explanation is the contrast of the light reflected on one surface compared with that of another, adjoining or adjacent surface. For example the contrast between the kitchen bench and the cupboard below and the wall behind.

Contrasts provide good visual cues and create greater safety especially in areas like the kitchen and bathroom. Lee Wilson lists the many things in and around the home and public buildings that need such contrast. He explains in more detail everyday items that we might not think of: coat hooks, locker handles, buttons, switches, toilet seats, floors/walls, and more.

There’s a more technical look at luminance contrast and compliance with standards on the EqualAccess website. It covers some of the most common errors and where things go wrong.  

 

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