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Figure 10-28.Process control chart
Contact Printing - 14209_286

Photography (Basic) - Introduction to photography and other graphic techniques
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CHAPTER  11 BLACK-AND-WHITE  PRINTING In photography, printing is the term used to describe the process of making positive images from negatives (and in some instances, from film positives). The most familiar example is the print made on a paper base. A photographic  print  is  made  by  passing  light  through  the negative   onto   a   piece   of   paper   coated   with   a light-sensitive emulsion, very similar to film. The two primary methods of making photographic prints  are  contact  printing  and  projection  printing. The principal difference in the two methods is the method of exposing the paper. In contact printing, the paper is physically in contact with the negative; while in projection printing, the paper is separated from the negative, and the image of the negative is projected onto the paper by a lens. Because projection printing is usually  used  to  produce  an  enlarged  image,  it  is generally referred to as enlarging. Contact printing produces positive images that are the same size as the negative  images.  Enlarging  usually  produces  positive images that are larger than the negative image; however, because optics are used in projection printing, the image formed on the paper can also be made smaller or the same size as the negative image. The  quality  of  the  photograph  can  be  varied  during printing  through  the  choice  of  printing  material, exposure, and processing. In printing, some negative defects may be compensated for, thereby eliminating the reproduction of the defect in the print. A well-planned, black-and-white or print room should  have  at  least  the  following  material  and equipment arranged properly so the flow of work moves easily from one stage to another: A contact and/or projection printer (enlarger) A sink large enough to accommodate the largest trays used in the print room Safelights A set of print trays A  graduate A   thermometer Print    tongs A wall clock with a second hand Hand    towels Photographic  printing  papers  are  predominantly blue and green sensitive and may be processed under the appropriate  safelight  conditions.  Consult  the  data  sheet packaged  with  the  paper  you  are  using  or  the Photo-Lab-Index for the recommended safelight. A minimum of three trays are needed for hand processing prints. The trays should be arranged in the sink from left to right-one each for developer, stop bath, and fixing bath. The ideal setup has five trays-one each for developer, stop bath, first fixer, second fixer, and a water rinse. This setup saves chemicals and results in better  fixing  of  prints. The  chemistry  used  to  develop  and  fix  prints  is similar  to  and  serves  the  same  purposes  as  film processing. When processing conditions are controlled carefully,  the  processing  specifications  recommended by manufacturers for their printing papers can be used to  provide  excellent  and  consistent  results. The print developer used most commonly in Navy imaging facilities is the llford Multigrade developer. The recommended tray processing developing times vary with the type of paper and developer being used. With  the  developer  at  68°F,  resin-coated  paper development is complete in about 2 minutes. The image appears in about 30 seconds. Because developer is incorporated in the paper, the useful capacity of 1 gallon of Ilford Multigrade developer (diluted 1:9) is about 400 8x10  prints,  or  equivalent. Any standard stop bath serves sufficiently. A stop bath may be used at all times, but it is necessary when processing a large number of prints; furthermore, the use of a stop bath after development prolongs the life of the fixing bath. If no acid is available for a stop bath, a water rinse  should  be  used  after  the  developer. A standard fixing bath should be used to fix the prints.  Consult  the  Photo-Lab-Index  for  the  various prepared chemicals available for fixing prints. Follow the manufacturer’s instructions when fixing prints because there are adverse effects in over-fixation as well as underfixation. Overfixation tends to produce thinning 11-1







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