Can You Convert Candela to Watt for Your Autocad Renderings?

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Discussion Overview

The discussion revolves around the conversion of candela to watts in the context of rendering light sources in Autocad. Participants explore the relationship between luminous intensity (candela) and power (watts), particularly in relation to typical light bulbs.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant seeks to convert candela to watts for a 60-watt bulb in Autocad, questioning if such a conversion is possible.
  • Another participant cites a definition from Hyperphysics, stating that candela is defined as 1/683 watt per steradian, linking it to luminous intensity.
  • A participant attempts a calculation, suggesting that 1500 candela equates to approximately 2.19 watts, and proposes that 41095 candela would be needed for a 60-watt bulb.
  • Another participant clarifies that the luminous intensity in candela is dependent on the solid angle of illumination and notes that a 60-watt bulb does not emit 60 watts of light due to energy loss, providing a lumen value for a specific bulb as a reference.

Areas of Agreement / Disagreement

Participants express differing views on the conversion process and the relationship between candela and watts, indicating that the discussion remains unresolved with multiple competing perspectives on the topic.

Contextual Notes

Participants mention the need for understanding solid angles and lumens, which may affect the conversion process. There are also references to specific bulb characteristics that may not apply universally.

nicolasmarie
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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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From the hyperphysics site http://hyperphysics.phy-astr.gsu.edu/hbase/vision/photom.html

The candela is the luminous intensity, in a given direction. of a source that emits monochromatic radiation of frequency 540 x 1012 hertz and that has a radiant intensity in that direction of 1/683 watt per steradian.

Also from hyperphysics,

lumpow.gif


http://hyperphysics.phy-astr.gsu.edu/hbase/vision/lumpow.html
 
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?
 
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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