Candela to Watt Conversion

  • #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?
 

Answers and Replies

  • #2
dlgoff
Science Advisor
Gold Member
4,322
2,596
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
 
  • #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?
 
  • #4
dlgoff
Science Advisor
Gold Member
4,322
2,596
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.
 

Related Threads on Candela to Watt Conversion

  • Last Post
Replies
1
Views
10K
  • Last Post
Replies
5
Views
33K
  • Last Post
Replies
4
Views
3K
Replies
18
Views
26K
  • Last Post
Replies
3
Views
3K
Replies
4
Views
49K
Replies
3
Views
2K
  • Last Post
Replies
19
Views
10K
  • Last Post
Replies
21
Views
46K
  • Last Post
Replies
12
Views
6K
Top