An Investigation into the application of digital camera created images and their preparation for newspaper lithographic reproduction without a reference analog reflection or transmission original

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Title: An Investigation into the application of digital camera created images and their preparation for newspaper lithographic reproduction without a reference analog reflection or transmission original
Author: Arocho, Victoria
Abstract: Looking at the shoes that digital photography has a role in filling we can quickly see performance issues that will undoubtedly affect our final printed reproduction. The resolution provided by a digital image is directly correlated to the CCD size, quality and any associated post-imaging processes provided by cam era manufacturers but is only one of quality-limiting factors involved in digital photography. "Silicon-based CCD's are monochrome in nature."' Having the inability to decipher the varying degrees of red, green and blue light presented to the pixels it is necessary to account for RGB light by introducing a color-filtering method. The color-filtering method prevalent in the cameras to be tested are referred to as "integral color filter arrays (CFA)."2 Integral color filter arrays performs color filtering on the chip with each individual pixel hosting a specific filter color (red, green or blue). This allows for the deciphering of the various light wavelengths presented in a scene to be translated by the CCD into digitized values of color, but because each pixel can only represent one filter color this results in problems including; "the loss of information leading to reduced effective resolution and increased sampling (quantizing) artifacts."3 Such color-gathering techniques and various inherent CCD issues account for problems that must be addressed and minimized during post-image processing prepress steps. The following endeavor is to evaluate three types of digital cameras (Minolta RD-175, Fuji 505a, AP NC2000e/Canon DCS EOS3) which can meet the requirements of a photojournalist then identifying the various issues that are inherent to each camera, post processing prepress solutions will be sought through the use of Adobe Photoshop. By evaluating the cameras via tests that provide information about resolution, dynamic range, color gamut reproduction abilities and image-to-noise relationships it was possible to assess what cam era shortcomings must be addressed during post-image processing. The shortcomings were then individually assessed and, utilizing prepress skills post-processing procedures, were identified to address the specific inherent shortcomings. Using SNAP (specifications for non-heat advertising printing) specifications, a representative set of images were printed and analyzed. The results from this analysis presents camera performance issues prior to post-image processing optimization and after post-image processing optimization. It will illustrate the initial shortcomings and how well these shortcomings can be de-emphasized in Adobe Photoshop. The printing of test images to SNAP specifications also illustrates if there is any loss of quali ty due to the reproduction on newsprint. Based on the test performed it was established that each usable camera ISO has its own specific set of characteristics that effect visual resolution, color gamut, usable range and noise. The method the man ufacturer uses to acquire its images, including CCD hardware, camera firmware and pre-acquire pro cessing, also affect visual resolution, color gamut, usable range, noise and aliasing. Photographic metering techniques and photographer criteria for ISO selection can assist in main taining the highest level of exposure quality capable for each camera. When the highest level of image quality is achieved with the use of photographic techniques, the highest level of visual resolution, color gamut, usable range and the least noise can be rendered for each camera image. Knowledge of Adobe Photoshop and offset printing principles, such as memory colors, wanted and unwanted colors, are valuable in enhancing the digital camera's limited color gamut. The nature of the newspaper printing process produces a small color gamut, therefore, the limited gamut inherent in the digital cameras is of less concern than if the digital images were printed using a larger color gamut capa ble four-color process. The identification of each camera's tendencies does allow for a greater understanding of applic able procedures within Adobe Photoshop which can reduce and or alleviate the tendencies.
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Date: 1999-11

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