FAQs

How you normally do.

Yes. That is why it is important to take the photo in a way that represents your viewing angle.

• For standard stairs, between 30^o- 50^o

• For ramps 0^o – 30^o

There is no need to zoom the photo, unless the subject to be measured is very small.

No, unless you wish to replicate a higher level of illumination for your contrast measurements. (Increasing light levels improves the luminance).

The photograph shows what we see, (or not), reflecting conditions experienced by users. It captures shadows, glare and reflections. For example, a curved surface will capture light differently and might be partially shaded. The information in the selected area is analysed, and variations are averaged out to provide a measure of luminance as it is experienced.

Different countries have adopted different approaches to measuring luminance contrast. The choice of calculation method can have a significant impact on the contrast result. Similarly, each country has set minimum requirements depending on the specific application. Some Standards require a minimum lux level, differences for large areas, small areas, hazards. Others have different requirements for different types of feature, such as tactile ground surface indicators (guiding blocks) and so on. It is important to use the standards within your jurisdiction.

The algorithm to calculate luminance as-we-experience-it has been validated. Results may vary due to:

· Chosen luminance contrast calculation method

· Prevailing light conditions

· Device dependency

A photometer can be defined as an instrument for measurement of intensity of visible light, so not strictly, but we can derive photometer readings in CD/m² if we measure lux levels as well. This was one of the validation methods for the algorithm.

Not strictly, but Get Luminance uses the image data to derive luminance. The main difference is that colorimeters are typically specular component inclusive with a controlled light source and measure pure colour by a sensor touching the specific surface. Get Luminance is specular component exclusive, which means it includes for prevailing light conditions and measures luminance from the colours as people experience them.

Yes, but not obviously. As per AS 1428.4.1 clause E3.3(e) “A more accurate calculation might be based on the relative proportions of each colour (where these proportions might be determined by image analysis techniques)”. Get Luminance uses image analysis.

Device dependent means that the readings obtained will vary between individual devices. This is just like a camera, video recorder, TV display, computer monitor etc. Indeed, it is also true of any photometric and colormetric equipment which work to agreed error levels and require calibration.

There is no need to white-correct luminance values.

Get Luminance can be used to help determine if further advice is needed and is not a substitute for the expertise of built environment professionals, access consultants or specialist testing companies.

The purpose of Get Luminance is to provide an everyday tool and an empirical basis for instructing further testing as needed.