Advances in High-Resolution Lithography

Recent advances in thermal lithographic plate imaging and continuous improvements in modern lithographic presses and printing materials have enabled Faust Printing, Inc. to produce a conventional lithographic print at a halftone screen ruling of 1110.80 lpi, probably the highest screen ruling yet achieved by conventional lithography. This paper describes the stages and hurdles that led Faust Printing to this achievement. This paper also provides photomicrographic comparisons of the Faust print with three other examples of high-resolution lithography. The question is framed whether an observer can perceive the improved resolution of very fine screen halftones. An experiment was conducted to compare printed reproductions at four screen rulings: 133, 175, 300, and 600 lpi. Participants ranked four sets of images in order of overall quality. The results were mixed. The images were ranked in order of their screen ruling for some pictures, but when the average rankings were examined there was no improvement in ranking for the 600-lpi prints compared to the 300-lpi ones. It seems that for some pictures observers can perceive an overall quality improvement with 600-lpi pictures, even though they cannot distinguish dot structures over about 150 lpi. No test was made to determine if the difference between 600 and 1,110 lpi would be perceived as a further quality improvement by observers.