A Study to Eliminate Moire Patterns Produced in Color Separations When Scanning Polachrome CS Transparency Film on the Hell DC-300 B/L Laser Scanner

The Polaroid Corporation, in May of 1983, introduced Polachrome CS color transparency film and a new process called the Autoprocess system. This system offers the convenience of obtaining instant color transparencies in about three minutes. The film has excellent projection and viewing characteristics. The product was designed to have its largest market with professional photographers. Polachrome\u27s construction creates problems for the printer in that moire patterns occur during the separation process. This study gives a short background for both additive color screen films and dye layer films, and a comparison is made to help the reader understand the problems with scanning Polachrome film. When attempting to scan Polachorme CS film, moire patterns are produced because of the color filters which make up the film. The emphasis of this study was to determine which scanner controls could be used to remove the moire patterns. Polachrome CS film is based on the principle of an additive color screen theory. The film contains many layers, one layer consisting of red, green, and blue filters which either passes or stops light. When this filter layer is viewed by the scanning lens an interference pattern called moire is produced by the variables of screen ruling, unsharp masking controls, and the angle of the transparency on the scanning drum. The hypothesis states that Polachrome CS color transparency film can be scanned on the DC-300 B/L laser scanner, so that separations are free of all moire patterns with acceptable definition. Pre-testing was necessary to determine which variables of the scanning process had an effect on producing a moire pattern. The results of the pre-tests determined the final choice of variables, which were then tested together. Defocusing, unsharp masking (intensity and starting point), as well as the angle at which the transparency is mounted, were determined to be the major variables that cause a moire pattern when scanning Polachrome CS transparency film. From the combination of these variables a total of 48 proofs were generated for the visual experiment. The visual experiment had two parts, involving 30 viewers, viewing the 48 proofs. Part I dealt with a question relating to moire patterns and Part II dealt with a question relating to the definition of the image. Data was recorded and analyzed. The hypothesis, that separations can be generated free of moire patterns with acceptable definition, was proven by 16 percent of the proofs tested. This resulted in a set of recommendations given as guidelines to follow when Polachrome transparency film is electronically scanned on the DC-300 B/L laser scanner

A tutorial in frequency modulation screening technology for lithography

An impressive diversity of opinions concerning many important aspects of the Frequency Modulation process are heard from users and vendors. It has not been difficult to catch a single vendor contradicting themselves within their own publications. Many of the claims vendors make are not supported by users\u27 experiences. Other users, on the other hand, have found many of the vendors\u27 brightest claims to be realistic. The information sought for this project was aimed to answer the question What can I expect if I implement Frequency Modulation screening technology in my shop today? In order to answer that question effectively, a clear and comprehensive understanding of the fundamentals of the FM process is required. The results and experiences of those that have had the opportunity to test the process are integral to a complete survey of the technology as it exists today. These requirements became the focus of this research effort. With limited access to any of the hardware and software necessary to implement an FM screen, research must necessarily be conducted by means of interviews, seminar attendance and surveys of recent publications. A list of questions was developed primarily out of the discussions at the GATF Technology Alert in Pittsburgh this past January and the Seybold Conference in Boston this spring. Both covered Frequency Modulated VI screening extensively. The GATF seminar was particularly helpful in developing a set of relevant questions that were shared by many of the users later contacted. Even among knowledgeable users and lithographic crafts people, the range of opinions on nearly every relevant topic covers the gamut of possibilities. A consensus among all of the sources included within this project on any major topic relevant to FM screening has proved difficult. The framework used here must therefore be flexible enough to accommodate contradictory opinions within its findings. Interviews were only conducted with experts recognized in the field and with users having first-hand experience in their own FM experiments. Testing and validation of the opinions and experiences reported here has not been part of this project, rather, the anecdotal experiences of many qualified users together are presented as a valid indication of what new users may expect when implementing the FM process. As it appeared that the range of possible answers to each question had been uncovered, the answers were formatted into short, self-contained bits of information. It is intended that a curious user be able to access complete chunks of knowledge contained within the document quickly without need for any supporting information (besides the requirement of familiarity with basic lithographic principles.) Most topics are less than a page. Some are more and a few are only short paragraphs. No first-hand verification of the information presented here has been attempted. By collecting the opinions and experiences of qualified users and researchers in the field familiar with the process, a body of knowledge is created which accurately reflects the state of the FM process as it currently exists and provides an answer to the question What can I expect if I implement Frequency Modulation screening technology in my shop today? Many early reports of FM screening implied that FM screening would soon sweep all of lithographic printing. As the realities and the difficulties involved in the process have become known and reported, it becomes apparent that a less enthusiastic and better balanced opinion indicates that FM screening can create a much improved print product though production difficulties make FM screening unlikely to gain wide use before dramatic improvements in the tools used to maintain process controls

Lunar Photo Study, Phase 4 Final Report, 30 Nov. 1967 - 30 Nov. 1968

Lunar photo stud

Aerospace Medicine and Biology: A continuing bibliography with indexes, supplement 165, March 1977

This bibliography lists 198 reports, articles, and other documents introduced into the NASA scientific and technical information system in February 1977