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Candela to Watt Conversion

  1. Sep 17, 2013 #1
    I am working on rendering in Autocad and I have came across light. A point light representing a bulb has intensity measured in candela, default value 1500 Cd. I want to represent a normal bulb of 60 watts used for a room. Is there a way to calculate Candela to Watt? Can anyody help me on this please?
     
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  3. Sep 17, 2013 #2

    dlgoff

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  4. Sep 17, 2013 #3
    Thanks. If I grasp something out of the definition, the candela is 1/683 of a watt through I totally have no idea about the steradian d even less concerning the lumens. 1500 candela is 2.19 watt i.e for 60 watts, i need 41095 candela. Am i correct?
     
  5. Sep 18, 2013 #4

    dlgoff

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    The luminous intensity in candela units is 1/683 per steradian where the steradian is the solid angle of one radian from the illuminating source. So you'll need to find the solid angle depending on what area you are illuminating. Check out this image:

    isqrr.gif

    http://hyperphysics.phy-astr.gsu.edu/hbase/vision/isql.html#c1

    Note that a 60 watt light bulb doesn't give 60 watts of light; there is going to be a lot of loss from heat. The box for the Philips soft white 60watt bulb I have in my hand says it has a brightness of 860 lumens. That's the value you should be using.
     
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