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#71
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PATRICK GAINER wrote
When I use HC110 for paper, I spice it up by adding some carbonate. The silver content of paper and the thickness of the emulsion can both be much less than those of film because light passes through the silver image twice. That "...light passes through the silver image twice" is the part that bothers me. Below you do not use that phrase. Below you describe what is actually going on. So, by absorbtion the light intensity is diminished once by transmission and twice by reflection. A good black will likely reflect from it's surface more light than will emerge from it's surface after two passes. That "much less" silver in a paper emulsion has me thinking of the "silver rich" papers on the market. Perhaps selenium's addition of mass to the image accounts for the deeper blacks on some papers. Good the subject came up. I'd given it no thought. Dan No, I'm saying that the same amount of silver per unit area will produce a higher reflected density than tramsmission density. All you have to do to prove that to yourself is look at a negative by transmitted light and then lay it on white paper and see how much darker it is. Thus, paper requires less silver per unit area to produce a given density than does a transparency. |
#72
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PATRICK GAINER wrote
When I use HC110 for paper, I spice it up by adding some carbonate. The silver content of paper and the thickness of the emulsion can both be much less than those of film because light passes through the silver image twice. That "...light passes through the silver image twice" is the part that bothers me. Below you do not use that phrase. Below you describe what is actually going on. So, by absorbtion the light intensity is diminished once by transmission and twice by reflection. A good black will likely reflect from it's surface more light than will emerge from it's surface after two passes. That "much less" silver in a paper emulsion has me thinking of the "silver rich" papers on the market. Perhaps selenium's addition of mass to the image accounts for the deeper blacks on some papers. Good the subject came up. I'd given it no thought. Dan No, I'm saying that the same amount of silver per unit area will produce a higher reflected density than tramsmission density. All you have to do to prove that to yourself is look at a negative by transmitted light and then lay it on white paper and see how much darker it is. Thus, paper requires less silver per unit area to produce a given density than does a transparency. |
#73
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"Jorge Omar" wrote in message ... Richard Out of curiosity, what kind of developers are used with these films (fine grin, high energy, etc) Thanks, Jorge (Richard Knoppow) wrote in om: Some films do have very thick emulsions because they are needed. The best example is the "film" made for nuclear track recording. Because the particles these films are intended to trace pass through the emulsion very efficiently the emulsion must be very thick to stand a chance of some particals colliding with the crystals in the emulsion. This stuff is very specialized and the conditions for its operation are very little related to normal pictorial film. Richard Knoppow Los Angeles, CA, USA I don't remember what Kodak used on their films, my memory is that its something along the lines of D-19. I do know that the fixer must be special and that these very thick emulsions are difficult to fix out and wash. -- --- Richard Knoppow Los Angeles, CA, USA |
#74
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Thanks again, Richard
Jorge "Richard Knoppow" wrote in news:2ofn51Fa9jl6U2 @uni-berlin.de: I don't remember what Kodak used on their films, my memory is that its something along the lines of D-19. I do know that the fixer must be special and that these very thick emulsions are difficult to fix out and wash. |
#75
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Thanks again, Richard
Jorge "Richard Knoppow" wrote in news:2ofn51Fa9jl6U2 @uni-berlin.de: I don't remember what Kodak used on their films, my memory is that its something along the lines of D-19. I do know that the fixer must be special and that these very thick emulsions are difficult to fix out and wash. |
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