Wa. Wagenaar et Jh. Vanderschrier, FACE RECOGNITION AS A FUNCTION OF DISTANCE AND ILLUMINATION - A PRACTICAL TOOL FOR USE IN THE COURTROOM, Psychology, crime & law, 2(4), 1996, pp. 321-332
This paper describes a practical courtroom tool that provides insight
in face recognition accuracy as a function of distance and illuminatio
n. Subjects were shown 3/4 target portraits with an exposition time of
12 seconds, immediately followed by a target-absent or target-present
lineup of six full-face portraits. Subjects were asked to identify th
e target. Seven distances (3 to 40 meter) and nine illumination levels
(0.3 to 3000 lux) were used which resulted in a 79 matrix, with in t
he cells a hit score and a false alarm score. From these rough data se
veral other measures were derived, like d-prime, diagnostic value and
some idealised scores. The scores represent the upper margins of recog
nition accuracy with the memory component reduced to a minimum. The re
sults clearly indicate a systematic increase of recognition performanc
e with decreasing distance and increasing illumination. The end result
is a practical rule of thumb, the Rule of fifteen: Even in ideal cond
itions the desired diagnostic value of 15 is reached at not more than
15 meters, not less than 15 lux.