When addressing the risk of laser-induced retinal injury in daylight, an individual’s pupil size (diameter) is of great importance since the retinal illumination varies as the square of the pupil size. Pupil size was measured under daylight conditions for 87 subjects to fill the data gap in over a century of laboratory pupillometry studies. Photography with a fixed chin/head rest and digital camera platform was employed to measure pupil diameter of subjects viewing a full-field neutral screen. The digital images of the pupils of 87 subjects were measured using computer software. Screen luminance values ranged between 790 cd m−2 to 4,300 cd m−2. The average pupil size for this study was 2.39 mm for an average luminance of 1,473 cd m−2. Pupil size measurements ranged from 1.44 mm to 3.03 mm. The data were stratified over luminance intervals, sex, eye color, and age.