Determination of image sharpness parameters of graphic art films using large-area densitometry

A method is described for deducing the image spread parameters of graphic a rts films from large-area density versus log exposure plots obtained by con tact exposures through a linear 'tint' test object. The success of the meth od depends on the high contrast and maximum density of the film, the design of the test object and the effectiveness of the antihalation layer. The me thod involves the calculation of the exposure inside and outside the geomet rical lines using light-scattering theory and the dependence of developed l inewidth on incident exposure. It is shown that the slope of the upper part of the developed linewidth versus log exposure curve depends almost entire ly on the optical properties of the film whereas the absolute value of the linewidth depends on both its optical and chemical properties. It is shown that the optical and chemical components of image spread can be determined separately from a single experimental curve of developed linewidth versus l og exposure derived from large-area densitometry. It is shown that the perf ormance of the antihalation layer can also be assessed from the same experi mental data.