Originally Posted by Vermilye
(the supplier of their fixtures) has changed the product from a 25 lamp unit to an 18 lamp unit.
According to the specification sheets on the fixtures, the newer unit draws slightly more amps (.05 amps more) and produces the same LUX (a measurement of light output on a surface). I don't understand the Lumen figures - the older double 25 lists a Lumen output of 154 while the newer double 18 unit lists lumens at 342. I'm not sure why the LUX would be the same unless the newer fixture is less efficient.
That link didn't work for me anymore; at the Kaper II
site I found likely fixtures in the Interior Lighting
category, and there are spec sheets for some of the products in the Technical Information area. I didn't see the double unit on this page.
"Lumens" are the measure of luminous flux - the total amount of light. The newer 18-LED unit apparently puts out much more light.
"Lux" are the measure of luminous intensity - the amount of light per unit of area
. This is why a typical spec sheet
shows a relationship between lux and distance. The newer 18-LED unit apparently spreads its greater light output more widely.
For instance, if the 25-LED unit put 154 lumens out and it spread evenly over four square metres at a set distance from the lamp, the luminance would be 154/4 lumens/m2, or 38.5 lux. If the 18-LED unit put 342 lumens out and spread it evenly over 8.88 square metres, the luminance would still be 342 lumnens/8.88 m2 or 38.5 lumens/m2, which is 38.5 lux.
The new lamp would make twice as big a table or counter just as bright.