Glaringly obvious

‘Glare’ refers to an uncomfortable sensation caused by a significant relative difference in brightness between ones focal point and a light source.

Physiologically, this is caused as the photopupillary reflex struggles to adapt the pupil to contradicting signals.  Initially, this will result in an uncomfortable sensory overload and typically the pupil will take around 5 minutes to constrict.  However, as the human eye only has a limited contrast ratio, this will leave the entire scene darker.

Continued exposure to glare results in fatigue, headaches and decreased workplace productivity. It doesn’t take much imagination to establish a direct link to profitability.

Myths & Contradictions

One of lighting’s big deceptions comes when comparing two identical installations with the same illuminance. Whilst the design tells us both areas are 300 lux, the eye may tell us one is up to twice as bright.

Conversely, the most glary and harshest light-source we will ever encounter is undoubtedly the sun.  Why then is an overcast day substantially less comfortable?  Surely diffusing the light always reduces glare?

Imagine riding a motorcycle on a sunny day without sunglasses down a twisting road. Despite the cornering and the distractions, the location of the sun is hard-wired into the human brain and a self-preservation instinct keeps our eyes averted (and therefore pupils appropriately adjusted).

Riding the same road on an overcast day, the entire sky is now a light-source which cannot be avoided. Your eyes and brain strain to cope with a light-source permanently in field of view as it focuses with constricted pupils on the road ahead.

Before 150lx / After 80lx