Measurements of photoplate transmission data require transformation into a relative intensity data set using some suitable representation of the relevant photographic calibration curve. Traditionally, this has been done graphically using either the Hurter and Driffield curve or various curve straightening functions such as the Seidal function. More recently, the availability of digital computers has permitted automation of this operation, and Burdo et al. have described an on-line system using a PDP 11/20 system with peripheral storage for this purpose.
L. S. Dale and R. N. Whittem, "A Simple Analog Computing On-Line Microdensitometer," Appl. Spectrosc. 30, 469-471 (1976)