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Census Microfilm Expeditors
sells the U.S. Federal censuses for $7.95 per roll. They use blue/black
diazo film and produce the guaranteed "Best Copy" available.
Silver microfilm has been designated as the preferred format for archival purposes. Though not as clear a film as diazo, its durability (75 - 100 years) has often made it the format of choice for research libraries. Diazo film is a cost-effective alternative to Silver. With a higher contrast image, diazo copies made from Silver Masters, are often of better quality than the original. With a shelf life of about 40 to 50 years they offer good durability at a much lower cost. Diazo film comes in two basic varieties: blue and blue/black. Blue/black is the preferred format for historical documents. Its higher contrast and darker overall image is superior to the standard blue film. Vesicular, a pale milky blue film, is easier for manufacturers to produce but its appearance generally leaves a negative first impression on customers. Surprisingly, it produces a relatively good image. So which film is to be preferred? In terms of price versus quality, blue/black diazo is hard to beat.
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