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2davidc8's avatar

Is an 800-lumen light bulb twice as bright as a 400-lumen one?

Asked by 2davidc8 (7691points) May 13th, 2017

I understand that the light output of light bulbs is measured in lumens. If so, my question basically is whether the lumen is a linear measurement. If this is the case, then an 800-lumen bulb is twice as bright as a 400, no?

Also, what is the relationship between lumen and watt? That is, how many lumen should an LCD bulb be rated at in order to appear as bright as a 60-watt incandescent bulb?

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4 Answers

MrGrimm888's avatar

A lumen is a measure of brightness. In America, incandescent bulbs used to be rated by “candlepower. ”

The LED bulbs are much brighter, and are measured by “lumens.”

The wattage is not as big a variable, as the brightness.

There are conversions for candlepower to lumens online.

Strauss's avatar

For most of the past 100 years, light bulbs were marketed and purchased by wattage rating. This was OK as long as they were all tungsten incandescent.

The FTC, in this press release, stated:

While watt measurements are familiar to consumers and have been featured on the front of light bulb packages for decades, watts are a measurement of energy use, not brightness…As a result, reliance on watt measurements alone make it difficult for consumers to compare traditional incandescent bulbs to more efficient bulbs, such as compact fluorescents.

Thevoice's avatar

Yes. At the very least, the first lightbulb may shine blighter than the other.

LuckyGuy's avatar

A typical 60 watt bulb puts out 500–750 lumens. Why the range? Because it depends upon the manufacturer, the components used and the age of the bulb. You can buy LED bulbs that are called “60 Watt equivalent”. They put out 750 lumens.

An 800 Lumen bulb puts out twice as much light as a 400 lumen bulb. How much of a difference it that? Well, not as much as you’d think. Our eyes are pretty clever devices and work over a wide dynamic range.
Here’s an experiment for you so you can tell. You will need an old camera that has a manual aperature setting. You will find the aperture labeled in f stops with numbers like:2, 2.8, 4, 5.6, 8, 11, 16, 22, 32. Each f stop lets in twice as much light as the number to its right. So 2.8 is twice the light of 4. 4 is twice the light of 5.6, etc. You will see that one f stop is not a big deal to your eye. It is hardly noticeable. If something is 4 times brighter you start to notice it but 2 times – not so much. .

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