Can You Convert Candela to Watt for Your Autocad Renderings?

[nicolasmarie]

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?

 

[dlgoff]

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,

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

 

[nicolasmarie]

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?

 

[dlgoff]

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:

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.

 

[alphy]

Yes, there is a way to calculate Candela to Watt conversion. Candela is a unit of luminous intensity, while Watt is a unit of power. To convert from Candela to Watt, you will need to know the luminous efficacy of the light source, which is the amount of light produced per unit of power. This value can vary depending on the type of light source. Once you have the luminous efficacy, you can use the formula: Watts = Candela * Luminous Efficacy. In this case, if the luminous efficacy of the bulb is 25 lumens per Watt, then 1500 Cd would be equivalent to 60 Watts. However, it is important to note that this conversion is not always accurate as the luminous efficacy may vary for different light sources.