Contrast reversal in photographic recording of laser radiation

An investigation was made of the action of 10^–8–10^–9 sec laser pulses in the presence of stray illumination of silver halide photographic emulsions commonly used in scientific research. It was found that sensitization or desensitization of a photographic emulsion with respect to the subsequent illumination could occur depending on the laser pulse power. In the case of successive or simultaneous recording of a high-power laser pulse and a low-intensity pulse representing background illumination, contrast reversal was observed for a certain level of illuminations and ratio of their intensities. When the order of recording was reversed, a negative image was always obtained.