I have a luxmeter, a 4ft twin lamp fluorescent shoplight, and a 4ft LED twin lamp shoplight replacement, so I did an experiment. I shut off all other lights in the room other than the one being tested and blocked off the window so there was no external sources of light.
The shoplight with reflector over my workbench has two relatively new F32T8 tubes each rated at 2800 lumens peak, 2660 lumens mean, for a combined output of 5600 lumens peak / 5320 lumens mean. I let the tubes warm up for 15 minutes to stabilize. Shoplight draws 63 watts from the wall. At 3 feet down from the light, dead center, holding sensor at arms length so I don't shade it with my body, I measured 1080 lux.
The 4 foot LED shoplight in the laundry area has two 180 degree emitter strips and is rated at 4000 lumens. It draws 40 watts from the wall. With the same 3 feet below, dead center, arms length measuing method as with the workbench light, I measured 1150 lux.
Hmm...if the LEDs perform WORSE on the light meter tests, where is all that light coming from? I believe the hype because I can see it with my own eyes and instruments.
You could have ten thousand raw lumens from a light source, but if only a tiny fraction of it gets to the right place, so much energy is wasted. For a shoplight, you want all the light projected downward onto the work area, but from a long and diffuse source such as a fluorescent tube or LED strip to reduce glare and shadows. For lighting up a living room, you want light that bounces off walls and ceiling, but you also don't need the same intensity as a workshop.
LED retrofits do encounter problems when the original space was set up for a brighter but less optically efficient light source. In those cases, the retrofitter should but often does not take measures to make up for the lost indirect lighting. However, in cases like this where more light on the work surface is desirable, LED retrofit is a good option.
The shoplight with reflector over my workbench has two relatively new F32T8 tubes each rated at 2800 lumens peak, 2660 lumens mean, for a combined output of 5600 lumens peak / 5320 lumens mean. I let the tubes warm up for 15 minutes to stabilize. Shoplight draws 63 watts from the wall. At 3 feet down from the light, dead center, holding sensor at arms length so I don't shade it with my body, I measured 1080 lux.
The 4 foot LED shoplight in the laundry area has two 180 degree emitter strips and is rated at 4000 lumens. It draws 40 watts from the wall. With the same 3 feet below, dead center, arms length measuing method as with the workbench light, I measured 1150 lux.
Hmm...if the LEDs perform WORSE on the light meter tests, where is all that light coming from? I believe the hype because I can see it with my own eyes and instruments.
You could have ten thousand raw lumens from a light source, but if only a tiny fraction of it gets to the right place, so much energy is wasted. For a shoplight, you want all the light projected downward onto the work area, but from a long and diffuse source such as a fluorescent tube or LED strip to reduce glare and shadows. For lighting up a living room, you want light that bounces off walls and ceiling, but you also don't need the same intensity as a workshop.
LED retrofits do encounter problems when the original space was set up for a brighter but less optically efficient light source. In those cases, the retrofitter should but often does not take measures to make up for the lost indirect lighting. However, in cases like this where more light on the work surface is desirable, LED retrofit is a good option.
