What is Photopic Lumens?
Photopic lumens refer 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 colorband. This is the light that is seen by the cone receptors in the eye and is called the “photopic lumens”. However, the rod receptors in the eye also receive light but it is the light rich in the blue portion of the spectrum. This light isn’t measured by the typical light meter. The combination of the light received by the rods and cones is called the “seeable lumens”. Therefore, the photopic lumens could be misleading when comparing different colors of light. Even though a lower lumen reading is obtained with a LED vs. HPS or Metal Halide, the LED will produce approximately 40% more seeable light.
