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  1. #11

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    Quote Originally Posted by Steve Smith View Post
    I think you need to forget about yellow and magenta and see how much blue and green you can get out of it and what grades you can get with these individually.
    Most probably, I will not be able to get really deep blue from an LCD projector, and a DLP-based projector should be better in respect to purity of color. Anyway, there is little need in extreme paper grades, at least in my practice.

    Vignetting seems to be another serious problem. In a normal enlarger we have somewhat abundant source of light. The limited rectangle of light from my digital mask will get darker towards its corners. There are two solutions for the problem:
    1. Digital. I can print a clear negative, scan the print and use it as a mask in PS.
    2. Analog. I can expose a piece of T-MAX, develop and use it on top of my negative carrier just like a center filter.

  2. #12
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    Quote Originally Posted by swilf View Post
    Anyway, there is little need in extreme paper grades, at least in my practice.
    That's exactly what I found with my LED enlarger. Grade 3.5 or possibly 4 was the most I could get.

    I think this is a good thing as if I need to go to grade 5 then I am not exposing properly or developing properly.


    Steve.

  3. #13

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    Quote Originally Posted by Steve Smith View Post
    I think this is a good thing as if I need to go to grade 5 then I am not exposing properly or developing properly.
    This sounds true regarding full frame. But sometimes it is necessary to print small part of the image with extreme contrast. A possible solution is to expose this part of the image with blue (or magenta) light filtered further through blue or magenta filter. Maybe I should always use light magenta filter in order to cut out some green from blue and get something like 1.5...4 instead of 1...3.5.

  4. #14
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    I imagine a diffusion type enlarger, where you project onto a translucent sheet above the negative.

    When you go to solve the close-focus problem, you might find that you still have to crop. Cropping might solve your light fall-off at the edges.

  5. #15

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    Quote Originally Posted by Bill Burk View Post
    I imagine a diffusion type enlarger, where you project onto a translucent sheet above the negative.
    I must admit that I do not have deep knowledge of optics, but it seems to me that focusing the projected image close to the negative plane is enough for the job. Sharp focusing, of course, is the thing to avoid here.

    Some cropping is tolerable as long as resolution of mask remains decent: say, 500x400 or so. Light fall-off still seems to be unaviodable.

  6. #16

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    Quote Originally Posted by Jadedoto View Post
    since most projectors and light based systems use RGB, you will not be able to get a true enough yellow and depending on the polarizing effect of the filters used, i doubt the crystals will turn enough to block other light you dont want..
    By the way, most projectors now use DLP instead of LCD. In short, white light is reflected from the matrix of micromirrors and then projected through rapidly rotating color wheel:

    http://en.wikipedia.org/wiki/File:In...Green_Blue.JPG

    It seems easy to attach a piece of 00 grade yellow gel filter to the surface of green sector and a piece of 5 grade magenta filter to the blue one. And to add some balance to the red sector to avoid vibrations.

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