Rapid access processing is a photographic processing method that combines high temperature processing and high energy developing agents to obtain very short induction periods, and thus, reduced processing times. In order to obtain maximum quality from the process, the rapid access halftone percent dot areas must be correctly evaluated according to established aim points. Traditional evaluation methods, either visual or instrumental, produce errors. These errors are the partial result of the unique dot characteristics of the process. These characteristics include soft, fringed dots; dots with low Dmax, found particularily in the shadow areas; loss of dot area on the tips of the halftone dots during plate exposure^ and high fog in the highlight areas. The illustration of the differences in dot fringe characteristics of a rapid access and a conventional lith halftone imaged with main exposures only were determined visually by the use of microphotographs illuminated with oblique illumination, and quanitatively by microdensitometer traces and film contacting the original halftone films, In all cases, the rapid access halftone dots: had a more highly fringed area when compared to the conventional lith halftone. The test designed to compare percent dot area of first generation rapid access halftones by zero referencing the dot area meter on the identified ghost dot to the percent dot area of their second generation hard dot contact films produced a poor correlation between the two sets of films. Of the three first generation halftones imaged with a main, main plus flash and main plus hump exposure; the main plus bump exposure produced the poorest correlation, particularly in the midtone area of the halftone scale. The compensation method designed to determine the effective percent dot area of first generation rapid access halftones by applying percent dot area correction factors found under various: halfone exposure conditions effectively reduced percent dot area error.
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School of Media Sciences (CIAS)
Gilliatt, John, "A Study of the Halftone Dot Characteristics of Rapid Access Halftones" (1983). Thesis. Rochester Institute of Technology. Accessed from
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