Q:

How many lumens do you need?

A:

Quick Answer

Ambient lighting for daily living activities in a bedroom or living room is rated 400 to 800 lumens per square meter. General room lighting for reading and work in a garage, kitchen or bathroom is rated 800 to 1700 lumens per square meter. Reading and detailed crafting is rated 1700 to 2800 lumens per square meter.

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Full Answer

Lumens are the SI unit of luminous flux, the total amount of visible light emitted from a source. The total light output of a luminous source is ineffective in determining the light rating needed to perform a certain activity, as the illumination per unit area is inversely proportional to the area for the same number of lumens.

Instead, lux, the unit of illuminance is defined as the number of lumens per square meter. This unit indicates the light intensity perceived by the human eye. Ambient lighting features a continuous spectrum of wavelengths with human vision having different levels of sensitivity to different wavelength ranges. A luminosity function determined by a standard model of human visual brightness perception is used to weigh the contribution of different wavelengths to the total illuminance of a light source.

The acceptable level of illuminance varies between applications, with more visually-oriented applications requiring a higher illuminance. The performance of very special visual tasks of low contrast and low size, such as surgery, may require between 10,000 to 20,000 lux.

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