A Method for Determining Halftone Dot Area using a Calibrated Visual Reference

A new method is proposed for determining halftone dot areas on printing plates, which uses only a calibrated visual reference and no instrumentation. This new approach to dot area measurement removes the uncertainty sometimes associated with measuring halftones with a reflection densitometer. The calibratied visual reference consists an exposure array of highly sensitive checkerboard targets. The key to the calibration lies in the fact that the exposures in the array differ by a factor which is tuned such that the dot area of the 50% dot will change by a known amount on the printed sheet. A visual comparison between the plate in question and the calibrated exposure array is all that is needed to confirm whether the plate is within a shop's specification for dot gain variation.