Illumination Photometers

Illumination Photometers Points : Illumination Photometers These photometers are used for the measurement of the illumination of surfaces. They may be required to measure the illumination in rooms, streets or playgrounds, and should be, in general, portable instruments.

The general principle of such instruments is that of the comparison of the illumination of a white matt surface placed at the point at which the illumination is to be measured, with the illumination of another surface forming part of the instrument, whose illumination is known and variable.

One of these is MACBETH ILLUMINOMETER. The operation of this instrument is based upon the inverse square law, and it is one of the most accurate instruments of this type. The normal range of this illuminometer is 1 to 25 Im/ft₂.

Another type of Lumeter or Luxmeter is HOLOPHANE LUMETER. Its range is from 0.002 to 8,000 lumens per square foot.