Contrast
"My vision is such that in certain light conditions, it is useless trying to use my vision at all, so contrast is important to me. In these situations, when light is insufficient, a contrast such as a different texture or colour is great. It is much easier to find a door if it is painted a different colour to its surroundings. That makes a power of difference. I also have been known to try to walk through a clear glass wall simply because I did not see it. That is why the application of some paint on to the glass is good. It is embarrassing if you are found trying to walk through a glass wall when the door is just to your left or right."
- Guide Dogs client
Contrast is the difference between one thing and another. For people who have impaired vision, contrast clues are useful for independent travel and for detecting potential hazards.
Contrast enables people to identify:
- Changes in level or slope;
- Unusual hazards;
- The most straightforward path through an open space;
- The location of a specific destination.
Contrast exists in different forms. The main types relate to colour, texture and luminance.
Luminance and Colour Contrast
Luminance contrast is the amount of light reflected from one surface or component, compared to the amount of light reflected from the background or base surfaces.
Colour contrast, meanwhile, is the difference between colours as they are positioned on a colour wheel. For example, violet is the contrast to yellow, and red is contrasted to green.
The perception of colour, however, can change with the type of light. Some people who have impaired vision are unable to see colours. Therefore colour contrast on its own may not be sufficient to provide a visual contrast.
The solution is to provide both luminance contrast and colour contrast in tandem, as together they more accurately indicate a contrast.
Effective uses of luminance and colour contrast include:
- Different coloured carpet, tiles or bricks to indicate the start and finish of a ramp;
- Street furnishings that contrast with their background when viewed from all directions;
- Contrasting door frames, doors, skirting boards and architraves to assist with locating doors;
- Contrasting paving at doorways to assist with locating the entry.
Luminance-contrast requirements in a given area should be measured under a variety of weather and lighting conditions.
Guide Dogs NSW/ACT advocates the use of higher luminance-contrast levels than recommended wherever possible. However, it is also important to avoid creating an overly busy or visually cluttered environment.
Tactile ground surface indicators have a range of minimum luminance-contrast requirements, depending on their composition and method of installation.
Over the rainbow
The United Kingdom's Reading University has developed a project called "Project Rainbow", which provides more detail about the use of luminance and colour contrast.
The University's Research Group for Inclusive Environments examined the needs of people who have impaired vision, and the colours that architects and interior designers can use to provide appropriate levels of luminance and colour contrast in buildings. This was balanced with the needs of other users.
Project Rainbow has published two design guides on the use of colour to assist people who have impaired vision to navigate the environment.
Luminance and Textural Contrast
The use of both luminance and textural contrasts maximises accessibility for people with vision impairment. The luminance contrast assists in recognising hazards while their textural contrast is equally useful. TGSI provide a good example of the combination of luminance and textural contrast.
The importance of luminance contrast is clearly demonstrated by glass doors and walls. Without a band of contrasting colour, people with normal vision often find them difficult to detect.
To prevent accidents, a coloured band used on glass should contrast sufficiently with the background surface. This may require the use of two different colours on either side, depending on the backgrounds. Consider, for example, a glass door at the entry to a building. When exiting the building, an asphalt road (dark grey) is seen through the door, and when entering the building, a pale wall is seen through the door. A contrast with the dark grey is required when exiting the building, while a contrast with the pale wall is required when entering.
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