Glare and Adaptation Effects Caused by the Miner's Caplamp:

Nearly all underground mine workers use individual caplamps with an intense central beam and a relatively dim surround. The small central hotspot (about 5–10 degrees in diameter) is over 100 times brighter than the wide-angle surround, creating an adverse ratio of luminances in the visual scene. Glare and transient adaptation caused by the hotspot make it difficult to see small or low-contrast visual targets in dimly lighted areas outside the hotspot.As part of a research program to establish minimum luminances for safe and efficient performance of various underground mining jobs, it was necessary to determine how the glare and transient adaptation produced by the caplamp hotspot affect visual performance in low luminance tasks in the mesopic region (0.03–0.30 cd/m2).If minimum luminance levels were determined with subjects fully adapted to low levels of even illumination, unrealistically low thresholds could be obtained due to the absence of the glare and transient adaptation effects caused by the ubiqui...