Reciprocity Law Failure in Photographic Exposures<!-- * -->

Reciprocity law failure is dealt with from the standpoint of its application to practical photographic exposures. Reciprocity failure and the manner of its portrayal are first briefly and simply described. It is then shown how the reciprocity failure diagram can be interpreted to show the behavior of time-scale and intensity-scale H&D curves, with regard to speed and contrast, for widely different ranges of intensity corresponding to those existing in certain definite classes of photographic work. Actual reciprocity curves for a number of commercial emulsions are included in the paper.