Intensity/Color/Distribution Rollout

Light—Pick a common lamp specification to approximate the spectral character of your light. The color swatch next to the Kelvin parameter is updated to reflect the light you select.

Kelvin—Set the color of the light by adjusting the color temperature spinners. The color temperature is displayed in degrees Kelvin. The corresponding color is visible in the color swatch next to the temperature spinners.

Filter—Use a color filter to simulate the effect of a color filter placed over the light source. For example, a red filter over a white light source casts red light. Set the filter color by clicking the color swatch to display the Color Selector. Default=white (RGB=255,255,255; HSV=0,0,255).

These controls specify the strength or brightness of photometric lights in physically based quantities.

You set the intensity of a light source using one of the following units:

lm (lumen)—Measures the overall output power of the light (luminous flux). A 100-watt general purpose light bulb has a luminous flux of about 1750 lm.

cd (candela)—Measures the maximum luminous intensity of the light, usually along the direction of aim. a 100-watt general purpose light bulb has a luminous intensity of about 139 cd.

lx at (lux)—Measures illuminance caused by the light shining on a surface at a certain distance and facing in the direction of the source. The lux is the International Scene unit, which is equivalent to 1 lumen per square meter. The AS unit for illuminance is the footcandle (fc) which is equivalent to 1 lumen per square foot. To convert from footcandles to lux, multiply by 10.76. For example, to specify an illuminance of 35 fc, set illuminance to 376.6 lx.

To specify the illuminance of a light, you must set the lx value, and enter the distance at which that illuminance is measured.

Note: You can obtain these values directly from lighting manufacturers. A table of some common lamp types is provided in Photometric Lights: Common Lamp Values.