A Comparison of Four Color Printing at One Angle and at Four Angles

Printing four colors: yellow, magenta, cyan and black at the same angle in offset lithography has exhibited characteristics that, in some cases, add flexibility and quality to the existing four color printing technology. This test involved a subject that was screened with six different screen rulings 100, 120, 133, 150, 175, and 200 lines per inch at one angle, 45 degrees, for yellow, magenta, cyan and black and at the conventional angles 45 degrees black, 75 degrees cyan, 90 degrees yellow and 105 degrees magenta. It was then printed on a 50 lb. coated paper on a four-color web press. The results show: 1. The one angle system did not perform as consistently as the four angle system for tone reproduction, except at 120 lines per inch. 2. The coarse line screen rulings 100k, 120, and 133 lines per inch at one angle exhibited more apparent sharpness than at four angles. 3. In the neutral areas of all the subjects at one angle, the interference pattern (the rosette) was eliminated, where as, the neutral areas of the subjects at four angles displayed an interference pattern. The results show: 1. The one angle system did not perform as consistently as the four angle system for tone reproduction, except at 120 lines per inch. 2. The coarse line screen rulings 100k, 120, and 133 lines per inch at one angle exhibited more apparent sharpness than at four angles. 3. In the neutral areas of all the subjects at one angle, the interference pattern (the rosette) was eliminated, where as, the neutral areas of the subjects at four angles displayed an interference pattern.