Does anyone know about scotopic ratios?

Question

it would be great to get some insight into this subject.

http://red-ridge.moonfruit.com/#/lightingscience/4530061096

Answer 1

I am assuming that you are actually looking at the scotopic to photopic ratio.

Eyes have two parts that are light sensing receptors - the rods and the cones. Light meters used to determine a lamps lumen output that are calibrated to only cone activated vision, the fovea (photopic) .  These light meters completely ignore the effect of rod activated vision (scotopic).  As a result, lighting practice accepted this single sensitivity function because it was erroneously assumed that the more light sensitive rods only functioned at very dim light levels.

Recent studies now show that rod photoreceptors are active not only in dim light but also at typical interior light levels as well.  Rods are more sensitive than cones to bluish-white light sources which is a characteristic found in higher color temperature light sources. This explains why environments using warm white (3000K) and even cool white (4100K) fluorescent lighting appear less bright than the same environment lit by lamps of a higher color temperature, 5000K or above.

Therefore, combining the Photopic and Scotopic lumen of a particular light source is more akin to how the human eye perceives light at normal interior light levels.

A higher ratio is said to reduce visual fatigue and disability glare as well as reducing energy costs because the same effective "brightness" can be achieved by a higher ratio instead of higher lumens, which require more energy to produce.