Understanding LED lumen output vs. HID lamps
Relating output lumens of an LED bulb to an energy source is not an precise way of measuring effective light output of a fixture. HID lamp lumens are measured spherically, including all lumens produced over the entire 360 degrees off the bulb.
Most light fixtures have to redirect much of these lumens back down to the target area, losing as much as 50% of the illuminating power in the process.
LED luminaires provide directional light output and have practically zero wasted lumens. Virtually every LED lumen is directed and placed to maximize efficiency. A more accurate evaluation is to measure actual foot-candles or LUX on the ground. HPS and MH lamps have a substaintial initial light output loss within the first 6 months. LEDs have no such drop and deliver useful light [with only 30% depreciation] for 12 to 15 years before needing replacement.
Measuring light effectiveness: Photopic vs. Scotopic vision
‘Photopic lumens’ refers to the amount of light emitted from a light source as measured by a light meter. The typical light meter is most sensitive to the yellow-green part of the color band. This is the light that is seen by the cone receptors in the eye, the eye’s cone activated or photopic vision.”
“However, the rod receptors in the eye also receive light, called rod activated or scotopic vision. This light, which is rich in the blue portion of the spectrum, isn’t measured by the typical light meter. Therefore, until now, lighting manufacturers have only measured light output based on the eye’s sensitivity to one type of vision (photopic).”
“A true evaluation of lumen effectiveness comes from the combination of the light received by the rods and cones (photopic and scotopic); or ‘seeable lumens.’ Therefore, measuring only photopic lumens is misleading when comparing different colors of light. This is why even though a lower lumen reading is obtained with a LED vs. HPS or Metal Halide; the LED will produce more "seeable" light.
See Photometrics for more information on light measurement and distribution.”
DIMMABLE from 0-100%
Unlike induction lighting or other HID technologies, our LED lights work beautifully with motion sensors; so when your lights are not needed -they don’t have to be on.
This further increases their lifespan and your energy savings.
Simply install motion sensors in areas which can get by with dimmer lighting when no one is there. When needed, motion sensors will turn the LED Retro-Fit Street™ on full strength instantly.