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Found 2 results

  1. First time post, be gentle. I want to bring my raw files from Monochrom into silver efex. SEP. But it will only accept RGB. Will this lead to loss of quality ? When I scan my black and white negs I do so in greyscale and that’s perfect for printing to black and white paper at Metro. It seems to defeat the object of the Monochrom if I have to convert to RGB ? Am I missing a trick ? What say you ?
  2. I was going through some old slides for scanning, and ran across this oddity. A slide shot on Polachrome instant color positive film. My hospital photo studio (the location of the photo) was a beta test site for Polaroid's instant 35mm technical films (Polaroid also made B&W continuous tone and B&W "lith" slide films that used the same process) which finally died in the mid-90s some time. Before somebody gets picky - yes, this is a pattern of color stripes, not the real Bayer checkboard RGBG. But they serve(d) the same purpose - to break up light into the primary colors so it could be recorded in one exposure on a single layer of monochromatic material (silver instead of silicon). The film was built backwards, with the plastic base facing the lens. The colored filter layer came next (in the color slide film), and then the silver layer on the very back (facing the pressure plate). The silver layer was surface-coated (so that it could react instantly with the processing chemicals without waiting for them to diffuse through gelatin) and thus was very fragile. Processing was done by putting the film, with a processing pack, into a light-tight processor rather like a bulk film loader, except that you wound the film IN rather than out. As the film was pulled out of the 35mm cassette by the processor, the pack smeared it with a chemical paste that reverse-processed the silver into a positive B&W image in about 2 minutes. The additive color filter bars meant that the silver layer was exposed in stripes based on the color of the light hitting it. Where blue light struck, the red and green stripes protected the silver, and it processed as black (no light) while the blue strip processed as transparent. Etc for each color. Thus on viewing the slide after processing, light was blocked by the silver from passing through the red and green stripes, but could pass through the blue stripes, revealing the subject matter as blue. The moire pattern on the wall is an artifact of digitizing the striped image - the stripes are about 2500 to the inch, so it would take at least a 5000ppi scanner (Nyquist frequency) to get a clean scan without the moire. Or blur it a little (homemade antialias filter). Anyway - an interesting oddity of film history, and a resurrection of the Autochrome color process from 100 years ago. Also interesting that Bryce Bayer at Kodak had patented his "sensing array for color imaging" about 7 years BEFORE Polaroid introduced Polachrome - so film and digital were running on two rails of the same track.
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