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  1. #11
    keithwms's Avatar
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    My solution for the monitor on/off flicker problem is simply to use a lower-sensitivity paper.... or reduce the sensitivity via a thin 'neutral density' sheet (which could serve the dual purpose of depixelating the light source).

    Note also that if you dither the screen (or the paper) even very slightly during exposure, the pixelation will be gone. Some high def monitors will dither for you. Dithering works as follows. Imagine two adjacent pixels, and suppose that you want to create a smooth gradient across them. You just vary the pixel values in time, and the average will be any intermediate value you desire. I am thinking that dithering is now so fast that one might be able to control exposures with it as well. I don't know how much residual luminescence is left on the screen, but my guess is that it is red shifted and thus wouldn't matter much for most papers.

    I did also consider a mechanical stage, with which you would slap the print onto the monitor and then pull it back, controlling exposure via good old inverse square law. I estimate that repeatable exposures as short as a 1/100 sec or so are possible that way.

    So... it's definitely doable. And of course the monitor controls all the d&b and contrast.
    "Only dead fish follow the stream"

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  2. #12
    ic-racer's Avatar
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    Even if you did get it to work, the results with a conventional film mask will probably be better.

  3. #13

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    Quote Originally Posted by ic-racer View Post
    Even if you did get it to work, the results with a conventional film mask will probably be better.
    Can you explain why you think this would be the case? What specific disadvantages would you see in this type of system, assuming the bugs were worked out of the exposure timing etc.

  4. #14
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    Quote Originally Posted by David A. Goldfarb View Post
    Along the same lines there have long been contact printers with something like 21 incandescent light bulbs that could be switched on or off individually for rough dodge/burn effects. Ansel Adams had a similar light source for his horizontal 8x10" enlarger, but I don't know if the bulbs were individually controllable.
    They were, by screwing them in or out.
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    Ralph W. Lambrecht
    www.darkroomagic.comrorrlambrec@ymail.com[/URL]
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  5. #15

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    Quote Originally Posted by keithwms View Post
    My solution for the monitor on/off flicker problem is simply to use a lower-sensitivity paper.... or reduce the sensitivity via a thin 'neutral density' sheet (which could serve the dual purpose of depixelating the light source).

    Note also that if you dither the screen (or the paper) even very slightly during exposure, the pixelation will be gone. Some high def monitors will dither for you. Dithering works as follows. Imagine two adjacent pixels, and suppose that you want to create a smooth gradient across them. You just vary the pixel values in time, and the average will be any intermediate value you desire. I am thinking that dithering is now so fast that one might be able to control exposures with it as well. I don't know how much residual luminescence is left on the screen, but my guess is that it is red shifted and thus wouldn't matter much for most papers.

    I did also consider a mechanical stage, with which you would slap the print onto the monitor and then pull it back, controlling exposure via good old inverse square law. I estimate that repeatable exposures as short as a 1/100 sec or so are possible that way.

    So... it's definitely doable. And of course the monitor controls all the d&b and contrast.
    Not sure any dithering would be necessary. As long as the monitor is not placed directly in contact with the film/glass, a short gap of 1/4-1/2 inch should provide enough diffusion of the pixels that it should not show any "pixelation" on the final print. I would venture that using a ground/etched glass for the contact glass may also help.

  6. #16
    keithwms's Avatar
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    Quote Originally Posted by PeteZ8 View Post
    Not sure any dithering would be necessary. As long as the monitor is not placed directly in contact with the film/glass, a short gap of 1/4-1/2 inch should provide enough diffusion of the pixels that it should not show any "pixelation" on the final print. I would venture that using a ground/etched glass for the contact glass may also help.
    I'm not as worried about pixelation as posterization of the tone emitted by the screen. If the tone curve of the mask isn't smooth then the silver paper will emphasize that for sure. My point is just that with dithering any tone can be rendered, even in the very worst case of only 1-bit white or black screen pixels.

    Anyway... it just has to be tried
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  7. #17

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    Keith, I would really like to pick your brain. However, it would be a waste of your time. Mine brain has grossly lost its plasticity and short/long term memory retention... much like a computer with a damaged CPU, inadequate/damaged RAM, and failing HD......

  8. #18
    keithwms's Avatar
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    Why don't you just upgrade and reboot...
    "Only dead fish follow the stream"

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  9. #19

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    I wish I could, Keith. Maybe the reboot will come soon enough though.

  10. #20
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    I've been using a technique developed by Alan Ross (as far as I know) to make masks. Start with a low res digital scan. make selections and fill them in with black on a separate layer. Adjust the opacity to get the right density on the mask. Print on transparency film at actual size. Place above the negative with a thin diffusion layer between. All the benefits of the high tech enlarger approach, but with minimal cost (assuming you own a cheap scanner, printer and computer). You can also print with yellow or magenta to control contrast in small areas.

    I had been making masks for a while with pencil on frosted mylar, but the computer makes this much more precise. It's amazing how well this works.

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