A good Luminance contrast can assist people with low vision in identifying important building elements such as Stairway Nosings, Doorways, Tactile Ground Surface Indicators and Signage in the built environment.
Light / Luminance Reflectance Value, or LRV, is a measurement of light that is reflected from a surface. Some of the ways to find the LRV are by means of a colorimeter, spectrophotometer or directly by the manufacturer (for example, LRV noted on a fan deck provided by a paint manufacturer).
LRV / Luminance Contrast is the light reflected from one surface as compared to the light reflected from another surface. This app calculates the percentage difference required when the LRV of any two samples are know. For example, if you have the LRV of the color of the door frame and the LRV of the color of the door, you can use this calculator to determine the contrast in % based on the formulas used in either USA or Australia.