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  1. #21
    keithwms's Avatar
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    Quote Originally Posted by Athiril View Post
    You do not need more dynamic range. That isn't the problem.

    What you want to do is actually reduce the dynamic range.
    We have a difference of definitions.

    In the manner that I use the terms, the 'dynamic range' of the film (and associated development process) is the number of zones that can be recorded, from toe through knee in the response curve. The brightness range of the scene is the 'scene brightness range' or SBR. Two very different things, of course.

    Anyway, I allege that a photochromic layer could fit a lot more SBR between the knee and toe. Again, the idea is to make graduated neutral density filters obsolete.

    I agree with the other comments that the response time of a photochromic layer could be problematic, but I can think of several straightforward ways to overcome this:

    (1) simply adjust the ISO of the film accordingly, through appropriate development i.e. pull processing; or,

    (2) place an appropriate neutral density layer between the photochromic layer and the film, so that the film receives less intensity per time; or,

    (3) place a shutter (or darkslide?) between the photochromic layer and the film and pull that after the photochromic layer has had time to respond...
    "Only dead fish follow the stream"

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  2. #22
    keithwms's Avatar
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    Quote Originally Posted by markbarendt View Post
    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.
    Yep.

    But I suppose that there is some merit to the idea of a multilayer emulsion, if the top one has some sort of incorporated developer that makes it grey up in the high intensity areas.
    "Only dead fish follow the stream"

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  3. #23
    Athiril's Avatar
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    I don't have my own definition, as I use the actual pre-existing definition of dynamic range. Which applies to everything.


    Recording the entire dynamic range like that will not help you, everything will simply be flat, dull and low contrast. The intensity of two separate areas will remain distinctly different, the dynamic range of the sky for example will map to light grey to medium grey, the dynamic range of the foreground will map to medium grey to dark grey.

    Instead of both being near white to near black, which is high contrast.

    Masking reduces your dynamic range, and balances these different parts closer together and thus increases their contrast when reproducing their entire dynamic range. Pull developing does not. It lowers your contrast.


    Basically, what you want, is for local contrast to exceed area to area contrast, which isn't there unless it's masked (like a grad ND) and the area to area contrast is reduced below local contrast.


    It may be possible to achieve that in developing.

  4. #24
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    Interesting idea. I have no way enough knowledge to really comment on this, but what I think you are getting at is a film that controls the light in such a way that the image it produces when developed without special techniques looks like those strange HDR images that litter the net that look unnatural but in the same way when done well somewhat intriguing where the dark foreground and bright background are all perfectly exposed.

  5. #25
    Athiril's Avatar
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    Speaking of strange HDR, I've had halo'ing with Rollei ATP.

  6. #26
    keithwms's Avatar
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    Quote Originally Posted by Athiril View Post
    Speaking of strange HDR, I've had halo'ing with Rollei ATP.
    What's your dev process? Are you agitating enough?
    "Only dead fish follow the stream"

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  7. #27
    keithwms's Avatar
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    Quote Originally Posted by mr rusty View Post
    Interesting idea. I have no way enough knowledge to really comment on this, but what I think you are getting at is a film that controls the light in such a way that the image it produces when developed without special techniques looks like those strange HDR images that litter the net that look unnatural but in the same way when done well somewhat intriguing where the dark foreground and bright background are all perfectly exposed.
    Well, of course, the idea is not to make an unnatural digital look, but rathert to mimic what our eyes actually see.

    Because of the pupil reflex, we see in HDR: our eyes automatically adjust for shadows when we look at them, and also for highlights when we look at those, and so the brain puts it all together into an HDR image... in a sense. No nasty halos or weirdness!

    Because it would be at the plane of focus on the film, what I am describing would be an extremely fine-detail mask and unlikely to appear unnatural. Just think of it as a very finely graduated neutral density filter that configures itself right where you need it.
    "Only dead fish follow the stream"

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  8. #28
    Athiril's Avatar
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    It's chemical exhaustion in your eyes behind the lens, they will exhaust to anything intense where luminosity or chroma (colour) and the resposne to that will drop, so it's masking + colour balancing somewhat. Open photoshop, and make one white layer, then a bright cyan layer above it, then full screen photoshop, stare at the cyan layer for 1 minute, turn it off, the white layer will not look white.

    A 'fine detail mask' will just serve to cancel out (partially) the image. And will actually do the opposite of the results you wan't. It will not change the response of the film of a bright to dark area, that'll remain the same, but within the bright area, it's own contrast of fine details will be masked down,

  9. #29
    Photo Engineer's Avatar
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    Kodak made a B&W film with 2 emulsions in it. One was very fast and the other one was very slow. This method was used to allow photographing nuclear explosions and allowed extreme range so that details could be seen through the bright flash. The demos that I saw were photographs of a light bulb in which you could see the filament and the bulb and the glass through the bright glow of the bulb.

    The original Kodacolor negative film had a B&W mask in it to extend the dynamic range and also to effect color correction. This was changed to the color mask which corrects color, and if you plot the curve it shows some degree of doing what is described here.

    The problem with all of these is the fact that they did not do as good a job as using 3 or more emulsions in one coating and extending the range that way. So, today's films use the blended emulsion route to attain a range of up to 5 or more stops. The color mask probably helps a bit though.

    Sorry I missed this. I was at a workshop for 3 days also tied up with a lot of other things.

    PE

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