A Study of mechanical dot gain for different dot shapes based on the border zone thoery

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Title: A Study of mechanical dot gain for different dot shapes based on the border zone thoery
Author: Sun, Kuang-Hua
Abstract: Mathematical equations have been derived to calculate the relationship of the dot area and the radius or diameter of a halftone dot . Dot gain is directly associated with the perimeter and the shape of a halftone dot. It is important to study the relationship between dot gain and dot shape, and to understand how each affects the printing result . The border zone theory explains that when dot gain occurs, the width of the border zone around the dot is constant and is independent of the dot shape and dot area. Four halftone gray scales with different dot shapes were made by a series of photographic processes. Both film contacting and a press run were employed to determine whether the border zone theory is valid. A transmission densitometer and an image analyzer were used to measure the dot area on film, plate, and press sheet. The final result of this study does not support thevalidity of the border zone theory. Different dot shapes do have different dot gain functions. The diamond-shaped dot in this study has the most dot gain around the quarter-tone. The square dot and round dot model 1 of this study has the most dot gain around the middle-tone, while the shape of round dot model 2 has the most dot gain around the three-quarter-tone. These findings indicate that printers should take dot shape into consideration when they perform the halftone process.
Record URI: http://hdl.handle.net/1850/11209
Date: 1991-05

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