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Calculating Light Level at a Point

  1. Nov 15, 2007 #1
    I haven't used my high school physics education in a really long time but I need to here at work for a very simple problem. I am an urban planner and we deal with lighting regulations a lot. I am trying to calculate the light level (in footcandles) at a given point. I am using the following general equation:

    [footcandles] = [light level in lumens of the source light] / [direct distance from point to light source]^2

    All I need to know is what units do I use to measure the distance? Meters, feet, inches? Would I measure the distance in feet since my light unit is footcandles? I know the standard scientific measurement unit is meters or some derivation there of, but I wanted to ask here just to be sure. Many thanks in advance.

    Last edited: Nov 15, 2007
  2. jcsd
  3. Nov 15, 2007 #2


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    Feet. A footcandle is defined in units of lumens/ft^2.
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