TECHGuru

  Imaging photometers refer to instruments that measure the luminous intensity of a light source, by comparing it with the standard source. This comparison could be done with a photoelectric cell (Pritchard photometer), or with the human eye (SEI exposure photometers or Lummer Brodhun). In flicker photometer, the visual photometer observer sees a field illuminated alternately with two sources which are to be compared. Once the flicker sensation disappears, the intensity of the test source could be concluded by reading the reference standard source with which it is compared. To determine the difference, frequency of alteration at a point which is below critical fusion frequency, but for the determination of distinction in the color or color difference, the frequency of alteration is chosen at a point which is above the critical fusion frequency. In other words, imaging photometers refer to instruments which find application in measurement of light intensity and understanding optical...