Abstract

The number of possible reproducible colors in a printing method is called the color gamut. This gamut is the range of colors around the spectrum and from light to dark that are available in the process. Previous research has found that the three parameters, spectral reflectance of the ink, solid ink density level and screening method, all influence the gamut in process color printing. This thesis evaluated how much these parameters change the color gamut both as individual parameters and in combination. A test target with 168 patches in the most saturated combinations of cyan, magenta, yellow and black was printed and measured with a spectrophotometer. The three coordinates L*, a* and b* for each patch in the target was plotted in the CIELAB space. Connecting these points forms a three dimensional object, the color gamut volume. By calculating the volume of this object the number of CIELAB combinations that can be reproduced in the system was derived. The pressrun was made at three levels of solid ink density and the targets were screened using frequency and amplitude modulated screening. The print was made on the six color Heidelberg Speedmaster 72 sheet fed lithography press at School of Printing Management and Science, Rochester Institute of Technology. The inks that were used in the test print are the Naturalith process cyan, magenta, yellow and black from Sun Chemical. In addition to these, a fluorescent magenta and yellow ink from DayGlo's ink series Starfire were used. These alternative magenta and yellow inks were printed with the Naturalith cyan and black. In this way two four color process combinations were evaluated with only six inks. The prints where made on a glossy coated paper, Centura Gloss from Consolidated Paper Inc. The result show that: Fluorescent inks can be used in process color printing and that they produced a color gamut that reproduce light and more colorful colors than normal process colors, while dark colors were reproduced with lower colorfulness. The fluorescent inks that were used are semi transparent and can not yield a dark black when printed on top of black. The solution is to use a high degree of under color removal and or to printing black as the last down ink. High solid ink densities was found to increase the color gamut for both ink sets. Frequency modulated screening was found to reproduce a color gamut with significantly higher gamut for the normal sheet fed inks, while no increase could be found for the fluorescent inks. By using frequency modulated screening and increasing the solid ink density when using normal sheet fed ink, the color gamut could be increased about 30 percent compared to amplitude modulated screening and SWOP solid ink densities. The Silicon Graphics based 3D software Explorer was found to be a very useful tool when determining the shape of the color gamut.

Library of Congress Subject Headings

Color printing--Research; Printing ink--Research; Screen process printing--Research; Colorimetry--Research

Publication Date

5-1-1997

Document Type

Thesis

Department, Program, or Center

School of Media Sciences (CIAS)

Advisor

Noga, Joseph

Comments

Note: imported from RIT’s Digital Media Library running on DSpace to RIT Scholar Works. Physical copy available through RIT's The Wallace Library at: Z258.A563

Campus

RIT – Main Campus

Download

Share

COinS