Luminance Contrast Calculators

Luminance Calculator: Bowman-Sapolinski Equation

This Luminance Contrast Calculator is to be used where the LRVs are known or determined by equipment specified in AS1428.1 & AS1428.4.1, including a tristimulus colourimeter or spectrophotometer. For example, two (2) paint colours from a Dulux colour fan deck or a similar deck. The LRVs for each colour are found in the rear of the fan deck. Please note that these LRVs are Spectral Component Inclusive, which means that the finish will affect the actually perceived contrasts.

The Luminance contrast ratio will be calculated automatically when the two (2) LRVs are entered into the cells. To calculate other LCs, simply enter the values into the cells.

This Calculator uses the Bowman-Sapolinski Equation as stipulated in AS/NZS 1428.4.1:2009

The Bowman-Sapolinski Equation Formula = 125 (Y2 – Y1) / (Y1 + Y2 + 25)
Where
C = luminance contrast
Y1 and Y2 = luminous reflectance values of the two surfaces

Instrumentation required to read Luminos Reflectance

A tristimulus colorimeter, or spectrophotometer with a diffuse illumination/normal viewing (d/o) geometry, is used with CIE Standard Illuminant D65. The instrument has to be capable of measuring absolute CIE for Yxy to be calculated. The measured luminous reflectance is defined by the tristimulus value Y. The chromaticity coordinates x and y provide an indication of the colour.