Editing Latent image (section)

===Low-intensity reciprocity failure (LIRF)===
Low-intensity reciprocity failure (LIRF) occurs when the crystal is exposed with weak light of long duration, such as in astronomical photography.

LIRF is due to inefficiency of forming a latent image, and this reduces photographic speed but increases contrast. Due to low level of exposure irradiance (intensity), a single crystal may have to wait for a significant amount of time between absorbing sufficient number of photons. In the process of making a stable latent image center, a smaller and less stable silver speck is made. Further generation of photoelectrons is necessary to grow this speck to a larger, stable, latent image. There is a finite probability that this intermediate unstable speck will decompose before next available photoelectrons can stabilize it. This probability increases with decreasing irradiance level.

LIRF can be improved by optimizing the stability of latent subimage, optimizing sulfur sensitization, and introduction of crystalline defects (edge dislocation).