It's more than just a difference in colour!!
The BCA and Australian Standards requires a number of building elements (short list provided below) to have minimum luminance contrast percentages. Luminance contrast is not simply a difference in colour, though colour does impact the percentages, it’s really the difference in the Light Reflectance Values (LRV’s). In other works, it’s the difference in how much light is being reflected off a surface compared to another surface. Luminance contrast plays a significant role in assisting people navigate through the built environment, just imagine how difficult it would be to get around if all the surfaces didn’t reflect any light at all – it would be impossible as you wouldn’t be able to see anything.
Luminance contrasting testing must be performed in line with the testing procedures as specified in Australian Standard 1428.1 – 2009 Design for access and mobility – General requirements for access – New building work – Appendix B3 & B5. Testing also compliant with AS1428.4.1 – 2009. Elements that must have luminance contrast are:
- Tactile Ground Surface Indicators
- Toilet Seats
- Glazing Strips
- Stair Nosings
- Street Furniture
It’s extremely important to note that the current versions of Australian Standards, that specifically address the testing of luminance contrast, are actually very difficult to actually achieve and are not considered to be the most accurate way to test luminance contrast. However with that being said – it’s the current way in which luminance contrast testing must be performed as in a legal setting it’s how it’s mandated as the testing methodology. Therefore ASN suggests that for the purposes of determining the most accurate luminance contrast percentages, it’s best to perform three (3) testing methodologies in both on-site and laboratory tests to obtain the LRV’s of building elements – these are:
Tristimulus Colorimeter Testing
The Konica Minolta CR410 is the only instrument that actually meets the requirements of AS1428.1 – 2009 & AS1428.4.1 – 2009 and therefore it must be used when testing luminance contrast. All other tristimulus colorimeters have an incorrect geometry and technically cannot be used in-line with what the Australian Standards requires.
The most important element to note about the Australian Standards that talk about testing luminance contrast with a Spectrophotometer is that the geometry that is specified is not currently available in any piece of equipment. The only geometry available is 45/0 – this although not technically meeting the Australian Standards is a suggestible more accurate way of testing as it is closer aligned with how humans actually see elements. It also factors in surface finishes etc.
This testing equipment is inclusive of ambient lighting conditions in the reading of the light reflecting. It therefore must be noted that as this reading or testing is effected by ambient lighting that it is highly variable due to the amount of available light at the time of testing. This type of testing should only be used in an onsite type testing.
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