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  1. #11
    keithwms's Avatar
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    Yes, I am aware of contrast masks, but my point is that with something like a photochromic layer, there would be no muss, no fuss. I don't believe the photochromics are all that complex to coat...

    Okay, I have the solution!!! A sheet of nice high-quality glass (or sapphire) coated with photochromics, and you just place that over the neg, with the photochromic pressed against the emulsion. Voila. This has to be tried

    http://www.ppg.com/optical/opticalpr...s/default.aspx

    Probably not neutral enough for colour film without some adjustment, but might be just fine for b&w.
    "Only dead fish follow the stream"

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  2. #12
    David A. Goldfarb's Avatar
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    For monochrome, printing out processes are generally self-masking. Shadows look good, but the highlights aren't there yet? Just keep exposing until the highlights are good, and the shadows will mask themselves, so they don't block up. This is a big attraction of albumen for me.

    It's not without its limitations. You still have an ideal density range for the negative, but it offers some flexibility and interesting possibilities that aren't otherwise available without contrast masks and careful registration.

    Color? Not sure if there is a self-masking tricolor printing out process, but of course if you're looking for something easier than contrast masking, a multilayer hand coated process with color separation negs ain't it.
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  3. #13
    Lee L's Avatar
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    Quote Originally Posted by keithwms View Post
    Yes, I am aware of contrast masks, but my point is that with something like a photochromic layer, there would be no muss, no fuss.
    Apologies. I misread. There was a reusable masking material as BetterSense mentions, but I've forgotten what materials it used.

    Lee

  4. #14
    markbarendt's Avatar
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    Quote Originally Posted by keithwms View Post
    I don't follow your idea, Mark- the exposed neg in the front wouldn't be cleared. Or am I missing something?

    But if there were some sort of transparent material with an integrated developer...?
    I'm saying, as an example, stack two sheets of film HP5 on top close to the lens and Delta 100 behind/away from the lens in a modified sheet holder.

    Set up and take a shot, the HP5 gets the normal exposure and the Delta gets the left overs after the light filters through the HP5.

    Separate the sheets.

    Develop the HP5 normally, develop the Delta reversed.

    Put the two sheets back together for printing.

    I have no clue if that combo would actually do the job and it would take some serious experimentation but theoretically the HP5 could be developed first and judged then the Delta could be developed as needed to get the total contrast into a printable range.
    Mark Barendt, Beaverton, OR

    "We do not see things the way they are. We see things the way we are." Ana´s Nin

  5. #15
    markbarendt's Avatar
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    The problem I see with the photochromic stuff I've seen is the time it takes to change.

    I don't know what it is called but for welding there is glass that instantly goes dark when an arc is struck.
    Mark Barendt, Beaverton, OR

    "We do not see things the way they are. We see things the way we are." Ana´s Nin

  6. #16
    Athiril's Avatar
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    You do not need more dynamic range. That isn't the problem.

    What you want to do is actually reduce the dynamic range.

    For a simple example, a sunset, the sky is very bright, and foreground not so bright.

    A high contrast shot becomes a low contrast dull image, a low contrast shot, becomes a high contrast vibrant image. When the whole range of the image is used from black to white.


    For a vibrant image, what you want in the simple sunset example is to have the dMin of the sky at X, and the dMax of the sky at Y, while in the foreground you also want' to have the dMin at X and dMax at Y, instead of X-Z and Y-Z etc.


    I've discussed a transition lens type setup between lens and film with several people, you can make one for a LF camera simply from a sheet of film, develop the sheet out, then weak bleach and then fix, and repeat, you want a few stops left, perhaps 1.0d or 1.3d, then you want a rehal bleach with chloride, to make a chloride emulsion in the dark, wash well, fix another sheet without processing, and wash well, stick that sheet against the emulsion side of the other sheet, in the dark, dry and take out in the light.

    In theory it should act like a silver chloride transition lens, and 'reset itself' in the dark, so you can insert it into a slot in a LF camera, and start pre-exposing it. Though you may not want to pre-expose it at the same focus as you're going to shoot. Depends... testing required!

    Of course the mask will be formed upon mostly from the UV and blue spectrum which may be a problem in several scenarios..


    edit: forgot to mention, you will need a copper source to go along with that new emulsion, or it wont work iirc. You could wash it in very dilute copper sulphate, or copper chloride perhaps before sealing it. Or use a copper bleach to begin with.



    Placing a light-formed mask right against the film will make a very defined mask, I do not think that will work how you want it to. What you need is a more general mask.

    For example, if you shoot a test chart.. black and white line pairs, a defined mask will just make the entire thing grey. You'll just lower adjacent contrast, not normalise large continguous areas. It needs to be more out of focus for that. Placing it further up the path might do that.
    Last edited by Athiril; 10-03-2011 at 11:50 PM. Click to view previous post history.

  7. #17
    polyglot's Avatar
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    For it to work in-camera, you'd need a really-fast printing-out effect. Which I think it pushing it a bit, to get anywhere near the densities you'd need with normal exposures, you need a development step.

    OTOH I have considered an auto-GND filter (applicable only to digital+tripod though); take a shot and have it rendered blurred in greyscale on a low-res LCD filter (bonus polarising effect) in front of your lens, then take the real shot.

  8. #18
    markbarendt's Avatar
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    I didnt explain my reasoning for the stacking and order well above.

    My thought is that you need a material with differing sensitivity thresholds to do what you want Keith.

    That was the thinking behind using a slower film behind a faster film.

    The Delta 100 in my example would theoretically be somewhere around three to five (or 7, I don't know) stops behind the HP5 (two for the rating plus whatever amount the HP5 acts like a neutral density filter).

    Once the threshold was reached the reversed Delta would in the end mask just the mid to low end of the HP5 curve and do it at a predictable rate.

    It would not be unlimited and require longer enlarger times.
    Mark Barendt, Beaverton, OR

    "We do not see things the way they are. We see things the way we are." Ana´s Nin

  9. #19
    BetterSense's Avatar
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    I don't know what it is called but for welding there is glass that instantly goes dark when an arc is struck.
    It's not a type of glass. It's an LCD panel.
    f/22 and be there.

  10. #20
    markbarendt's Avatar
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    I just figured out that I'm wrong in suggesting reversal of the one sheet. I think it should both should be negatives.

    A positive would just lower the contrast rate, a negative would maintain contrast rate and just add more density to the highlights.
    Mark Barendt, Beaverton, OR

    "We do not see things the way they are. We see things the way we are." Ana´s Nin

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