![]() ![]() If you like to convert lumens to watts to compare brightness by the equivalent wattage among standard bulb types, 40 lumens is approximately equivalent to a 4-8 w incandescent, or 0.4-1.5 w LED bulb. So if you must ask, how bright is a 40 lumens bulb? It is 40 lumens bright. Among all three aspects of lighting, only lumens are directly comparable while you need additional information to calculate the luminance or illuminance. This is why there is so much confusion about brightness that many customers may assume brightness means lumens and others might think brightness means luminance or illuminance. ![]() Only in the context of general service lamps, the brightness refers to lumens. This is because the FTC required the light output(lumens) of general service lamps to be expressed as brightness. For example, we would feel like saying my lamp is bright or my bedroom is bright, but we are practically talking about either luminance or illuminance.īut if you have ever bought a light bulb or a lamp, you have probably seen the lighting facts label on the package or product descriptions which use lumens as a measure of brightness. The three terms luminance, illuminance, and brightness are often used interchangeably. Illuminance is how well the surface is lit, but it was also formerly often called brightness. Thus luminance is an indicator of how bright is the light source. In this example, illuminance is the amount of light in the area of the table that was lit up by the lamp.īrightness is actually the term for the subjective impression of luminance, as it measures the intensity of light that can be detected by the human eye. Illuminance is the amount of light incident on a surface per unit area.In this example, luminance is the light emitted from the bulb in the lamp holder of the desk lamp. Luminance is the amount of light emitted by the light bulb per unit area in a given direction. ![]() No matter where you use the 40 lumens light bulb, it always outputs the same 40 lumens light.
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