Urban Velo

Candela? Lumen? Lux? What do they mean?


From Cantitoe Road:

It’s not possible to make a direct comparison among these units because they measure different things. For the purposes of cycling, Lux is what you’re looking for because it measures light intensity in a given area – the area in front of you which (we hope) is where you’re going.

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  1. ScottJuly 27, 2013 at 2:36 pm

    Your terms for lighting are not quite correct. All three are measures of intensity (AKA strength). Lumen is the base metric and describes total potential light energy emitted in all directions.

    Lux is as you stated illumination per area (lumens per square meter = lux). Lux values change with distance so lux is not typically used unless you know the distance from light to target and he size of the beam of light.

    Candellas are lumens broadcast in a particular direction (lumens per solid angle). Candellas (AKA center beam candle power) can be used to compare too spotlights with the same beam angle. For example 25-degrees at 1000 candellas.

  2. Lumens and Lux: Light Words Explained in a Single Image « Music RSSJuly 27, 2013 at 3:10 pm

    [...] above image, posted yesterday by a folks during Urban Velo, explains all we need to know about a common terms lumens, lux, and candela. They’re [...]

  3. iquanyinJuly 27, 2013 at 3:54 pm

    whats the difference between strength and intensity?

  4. AaronJuly 27, 2013 at 10:04 pm

    Scott above has it correct- CBCP is the value used in professional lighting calculations. All architectural and most theatrical fixtures have a CBCP value that can be used with the Inverse Square Law to calculate the lux (or footcandles) at a given distance. One Lux = 1 lumen per square meter; 1 FC = 1 lumen per square foot. 1 Lux = 10.76 FC as there are 10.76 square feet in a square meter.

    Although there are hundreds of thousands of light fixtures that have been tested an have light output data, none seem to be bicycle lights. It’s a shame that the bicycle light manufacturers would rather hide behind unusable data than provide meaningful information.

  5. Lumens And Lux: Light Words Explained In A Single Image | Gizmodo AustraliaJuly 27, 2013 at 11:00 pm

    [...] above image, posted yesterday by the folks at Urban Velo explains everything you need to know about the common terms lumens lux and candela. They’re [...]

  6. Name:Tom PetrieJuly 29, 2013 at 2:20 pm

    Lux is indeed the measure of light intensity in an area at a given distance from the light source. With Trelock lights, maximum brightness is measured at 10 meters with a light field of 4 meters in width. Click here for an illustration.

  7. Candela Lumen Lux | de veloJuly 31, 2013 at 6:58 am

    [...] aus: Candela? Lumen? Lux? What do they mean? http://urbanvelo.org/candela-lumen-lux-what-do-they-mean/ [...]

  8. JoshJanuary 22, 2018 at 12:53 am

    I believe the main takeaway here is that beam angle is very important. A bright light that does not project properly will not illuminate an object located any distance away.

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