Re:Energy saving light bulbs offer dim future
by ars on Sunday September 13, 2009 @06:08PM
(#820654)
More garbage science.
You can not measure lux when you are so close to the bulb, and lux is not the correct measurement for light bulbs anyway, lumens is.
Lumens: total light produced by bulb in all directions.
Lux: amount of light hitting a sensor, adjusted proportionally based on size (area) of sensor. (It's actually light per area.)
If you put the sensor close to the bulb most of the light from the bulb will bypass the sensor.
An incandescent is basically a point source of light, so putting the sensor close works fine.
Florescent is not, the light output comes from a large area. For the real world, unless you need a spotlight, this makes no difference, since you are illuminating an entire room. But if you try to measure with a small sensor you will underestimate the light output.
You can not measure lux when you are so close to the bulb, and lux is not the correct measurement for light bulbs anyway, lumens is.
Lumens: total light produced by bulb in all directions.
Lux: amount of light hitting a sensor, adjusted proportionally based on size (area) of sensor. (It's actually light per area.)
If you put the sensor close to the bulb most of the light from the bulb will bypass the sensor.
An incandescent is basically a point source of light, so putting the sensor close works fine.
Florescent is not, the light output comes from a large area. For the real world, unless you need a spotlight, this makes no difference, since you are illuminating an entire room. But if you try to measure with a small sensor you will underestimate the light output.