Seeing the Light with Luminance Contrast

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Tuesday, March 8th, 2016
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When we consider the need for contrasting surfaces in the built environment, there are some important terms we must understand from the outset.

International Standard ISO 21542 defines ‘luminance’ as the intensity of light emitted or reflected in a given direction from the surface element divided by the area of the element in the same direction. This value is expressed as a Luminance Reflective Value, or LRV.

ISO 21542 defines this LRV as the proportion of visible light reflected by a surface at all wavelengths and directions when illuminated by a light source. The LRV is expressed on a scale of 0 to 100, with a value of 0 points for pure black and a value of 100 points for pure white. Many reputable suppliers and manufacturers will provide the LRV of their products, including paint companies.

When we test the suitability of one surface against that of another we actually need to check that the luminance contrast (or visual contrast) is acceptable to aid in visual identification. Australian Standard (AS) 1428.1 defines luminance contrast as the light reflected from one surface or component, compared to the light reflected from another surface or component.

Typical surfaces to be tested for luminance contrast are floors, walls, doorways, key fixtures and fittings, signage, stair components and the like. In Australia, we have prescriptive requirements that require minimum levels of luminance contrast (LC) in the built environment. However, these minimum requirements are limited to the following:

  • the toilet seat needs a 30 per cent LC to the pan, floor or walls behind the pan when viewed from the doorway
  • Each stair tread needs a 50-millimetre to 75-millimetre wide nosing strip with a 30 per cent LC
  • Doorways need a 50-millimetre band providing 30 per cent LC (with varying options to achieve compliance, including between the door/jamb; door/wall; architrave/wall; architrave/door; or door jamb/wall)
  • Tactile ground surface indicators need a contrast to the floor surface, being 30 per cent LC for the integrated floor tile type; 45 per cent for single coloured discrete type (individual buttons); and 60 per cent for composite-discrete (two coloured button) type
  • Signage requires a 30 per cent LC against the wall background surface
  • Visual indicators (also known as glazing bands or manifestations) are needed for glazing panels capable of being mistaken for an opening. In Australia, a visual indicator glazing band requires a 30 per cent LC against the immediate floor surface (measured two metres from the glazing on each side).
  • Lift buttons require a 30 per cent LC around their edges, unless they are self-illuminated buttons

So what else can we do to create more accessible environments for everyone, and help to remove visual confusion? Well, ISO 21542 provides some practical recommendations that can easily be adopted into new projects:

  1. Ensuring that there is a minimum 30 per cent LC between a floor and the wall edges to assist wayfinding. In fact, this is a proposed requirement in the draft wayfinding standard.
  2. All toilet seats should have a 30 per cent LC to their background (not just the accessible toilets.)
  3. Urinals should have a 30 per cent LC visually with the wall to which they are attached.
  4. Fixtures and fittings in sanitary facilities should visually contrast with the surface they are fixed to, including coat hooks, dispensers, grabrails and sanitary disposal bins.
  5. Changing room coat hooks, locker handles, bench seats and other furnishings should have sufficient contrast to their backgrounds.
  6. Good lighting is required, with matte finished surfaces and furnishings.
  7. Providing oversized buttons and switches with 30 per cent LC to the walls or their surrounds.
  8. A contrast between door leafs and door handles.
  9. Increasing the LC to 70 per cent for potential hazards and text information.
  10. Providing not more than 20 per cent LC between colours and patterns on floor coverings to remove any potential visual confusion.
  11. Stair and ramp hand-rails should have a 30 per cent LC to the walls.
  12. Ensure all bollards, bike racks, columns and posts have a 30 per cent LC.
  13. The combination of any variables of reds and green should be avoided. Other potential difficulties for perception exist when using the colours green, olive green, yellow, orange, pink and red.
  14. Provide 150-millimetre high kerb-rails to both sides of ramps that achieve a 30 per cent LC.

These inclusive design and universal design principles help everyone identify key features of a building, providing a safer and more intuitive environment for everyone.

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