Scotopic Spectrum

Published February 2000

The visual efficiency curve for the pigment of the "rods" of the retina. It determines the size of the pupil; a small pupil will increase depth of field, increase visual acuity and decrease the amount of accommodation needed for near tasks. Thus, small pupils reduce "eyestrain." Many indoor lights such as incandescent, warm light fluorescent and especially sodium lamps are deficient in the scotopic part of the spectrum and thus may promote eyestrain. A good lighting system in the work environment bathes the area surrounding the task with scotopically rich light. (Note that color is not always a good indicator of the lighting spectrum. See the manufacturer's specification.)