about our lights » Pupil Lumens & Design Lumens
There are two distinct types of lumen output produced by lamps.
The first referred to as photopic or design lumens, represent the relative sensitivity of the eye under intense lighting such as sunlight. Photopic lumen output is light registered by the cones in the human eye and is measured by standard lumen and foot-candle meters.
The second type of lumens, called scotopic, represent the sensitivity of the eye under typical interior lighting conditions and cannot be measured directly with a standard light meter. Scotopic lumen output is the amount of light registered by the rods of the human eye and also controls pupil size directly effecting visual acuity for tasks.
For lighting interior spaces a correction factor may be applied to photopic lumen readings to find the usable light produced by a given light source, also called pupil lumens. Two different light sources having similar design lumen readings taken by a standard light meter can have drastically different usable light outputs and apparent brightness. A system producing more pupil lumens will be easier on workers’ eyes and in return boost employee morale.