Photometers are specifically designed to measure emitted, reflected or transmitted light in photometric terms of luminous flux, luminance, illuminance or luminous intensity. They utilize a single detector - usually a photomultiplier tube or silicon detector - and a filter that changes the system response to match the photopic function recommended by the COMMISSION INTERNATIONALE DE L'ECLAIRAGE (INTERNATIONAL COMMISSION ON ILLUMINATION).
Measurements of displays typically require results in luminance (footlamberts or cd/m2). Photo Research photometers feature the patented Pritchard optical system to clearly and unambiguously define the area to be measured.