Lighting/Illumination Studies

[Brian Dorr]

Can lighting/illumination levels be calculated at points other than the ground(i.e. 25ft or 50 ft in the air) for a site? What handbook or where would I fin direction on how this is done?
Also, can you discuss the difference in illumination from a 250W HPS mounted at 50 ft versuses a 400 metal halide mounted at 25ft.
thanks

 

[bcorbin]

Illumincance levels are calculated for just about any point or surface you can think of, but the lion's share of the calcs I do are at 3' above finished grade.

As for where to look for information on lighting, try IESNA. They are pretty much the final word on lighting.

 

[jtester]

Also, can you discuss the difference in illumination from a 250W HPS mounted at 50 ft versuses a 400 metal halide mounted at 25ft.
thanks

Light levels drop off with the square of the distance. For example if you have a fixture that produces X fc at 25', it produces X(25/50)**2 or X/4 at 50'. Determine the fc levels for each fixture at a given distance and use the above relationship to determine the level at another point.

Jim T

 

[Artemis]

Is it an interior or exterior application? Some lighting manufacturer's off free programs to specifiers, you might want to check them out, they are simple to use. Supply houses and lighting representatives will also do "point by point" lighting calculations at no cost and usually turn around simple projects in a day or two.