Extech lt4045 lux meter for standard lighting white leds and coloured leds extech lt45 the extech led lt45 light meter is used for monitoring and optimizing environmental light levels in buildings schools and offices led lighting is being used more commonly because they are less expensive more energy efficient and brighter the lt45 measures both white red yellow green blue and purple led lights manually storerecall up to 99 readings the lt45 is supplied with a light sensor with