Lumens Schmoomens

[jwilhelm]

Most manufacturere lighting data provides "footcandles" at various distances from the light and at various spread angles. Footcandles at a given surface is really what we need to know to specify lighting fixtures but in order to define them in Accurender we need to specify "Lumens", a measure of total light output of the lamp, for the purpose of creating photometriclly accurate light fixtures can someone give me a rule of thumb for setting Lumens to achieve a certain footcandle level on a surface. surely there is some formula for that, perhaps when they implement Accurenders lighting analysis software this will be easier to visualize, but it would be nice to creat accurate fixtures for rendering purposes to at least get close.

[beegee]

Footcandles (fc) = Total Lumens (lm) ÷ Area in Square Feet

so lm = fc/a

and if you want to get really serious ...

Required Light Output/Fixture (Lumens) = (Maintained Illumination in Footcandles x Area in Square Feet) ÷ (Number of Fixtures x Coefficient of Utilization x Ballast Factor x Light Loss Factor)

Remember, a foot-candle is how bright the light is one foot away from the source. A lumen is a way of measuring how much light gets to what you want to light. A LUMEN is equal to one foot-candle falling on one square foot of area.



hth.

[PeterJ]

Is there nothing you don't know?

[Roger Evans]

His wife's birthday.

[aggockel50321]

This site does a good job of explaining all about light. (http://www.squ1.com/ecotect/ecotect.html)

Look in the lighting design section.