Lighting Intensity Question ...

[Devilinity]

Whats the difference between the 3 lamp intensity type? Intensity (Candela), Flux (Lumen) and Illuminance (Foot-candles) ...

 

Try to keep the explaination simple please, cos I read the "help" explaination in the autocad program and it got me lost

[ReMark]

Candela: A unit of luminous intensity.

 

Lumen: One lumen is the amount of light emitted in a solid angle of 1 sr, from a source that radiates to an equal extent in all directions, and whose intensity is 1 cd. Huh?

 

Foot candle: A unit of illuminance on a surface that is everywhere one foot from a uniform point source of light of one candle and equal to one lumen per square foot.

 

Yep. Now I know why I didn't become an electrical engineer.

[shift1313]

http://acl.co.uk/light_level.htm

 

foot candle,

[shift1313]

Candela: A unit of luminous intensity.

 

Lumen: One lumen is the amount of light emitted in a solid angle of 1 sr, from a source that radiates to an equal extent in all directions, and whose intensity is 1 cd. Huh?

 

Foot candle: A unit of illuminance on a surface that is everywhere one foot from a uniform point source of light of one candle and equal to one lumen per square foot.

 

Yep. Now I know why I didn't become an electrical engineer.

 

 

 

Light intensity is a simple ratio, I = flux/watts. flux is measured in lumens, lumens in a steradian is called candlea(cd). Steradian is a unit of solid angle. Basically a beam ray, bad terminology. Think of the spot a flash light leaves on a wall in the dark. This pattern is a direct relation to the intensity and the distance. the flux is a measure of intensity in this area. Lumen is the measure of "perceived" power of light.

 

 

if you want to go any more in depth than that we have to start talking about sinusoidal functions and wavelengths of light and visible spectrum.

 

did that get it for you?:wink:

[ReMark]

Clear as a dim bulb on a foggy night in ol Londontown as seen from behind the barn by a one eyed man who just got a whiff of pepper spray. It was moonless night too.

[shift1313]

good so you got it

[Devilinity]

Light intensity is a simple ratio, I = flux/watts. flux is measured in lumens, lumens in a steradian is called candlea(cd). Steradian is a unit of solid angle. Basically a beam ray, bad terminology. Think of the spot a flash light leaves on a wall in the dark. This pattern is a direct relation to the intensity and the distance. the flux is a measure of intensity in this area. Lumen is the measure of "perceived" power of light.

 

 

if you want to go any more in depth than that we have to start talking about sinusoidal functions and wavelengths of light and visible spectrum.

 

did that get it for you?:wink:

 

So which of the 3 should i normally be using if i wanted to shine a light on a table or somethink?

[shift1313]

in 09 your light properties will have a photomertic tab where you set the intensity in Candela(cd). Then in the area above that you can set the intensity factor.

can you tell me where you are seeing these options and ill look through them a bit because all i see is an intensity factor and candela

[papagyi]

can you tell me where you are seeing these options and ill look through them a bit because all i see is an intensity factor and candela

You can see light properties dialog box if you will create photometric light.You can change light units (above said this thread )from light intensity drop down.

[shift1313]

papagyi, i created light and got to the photomeric tab but didnt see any option to change between what he is asking. but

 

ill have to play around with the setting since i only installed 09 last night and didnt have a chance to play with it but...

 

The difference in the 3 should only be how you input the intensity(again i havent played with it)

 

that first website i linked you too gives common light levels indoor and outdoor and explains a few things. all the way at the bottom it gives you numbers for offices etc. this is in lux, which is lumen/m^2. so if you have an area in your drawing you can multiply that by their number to give you the answer in lumen, which was one of your choices.

 

The 3 options are just different ways to measure the same thing(i think, now i dont know anymore:))

[papagyi]

You should set "lightingunits" "2" and you can create any light.Next select light and go to light properties dialog box and you can choose light intensity with (Cd,Flx,lum..etc).