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  1. #21
    holmburgers's Avatar
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    Three-color photography with a 2-color camera

    Quote Originally Posted by michaelbsc View Post
    I've been toying with the mechanics of trying to build one... Making a two color system at home isn't trivial either, or I'd be all over it. But it isn't outside the realm of hobbyist possibilities either. And a plate beam splitter and front surface mirror is a lot less expensive than getting the tri-color prism.
    Ok, so I don't know why it took me so long to put these two pieces together... but there's a very interesting idea presented by F.E. Ives that would make a two-color camera, as suggested by Michael, possible of creating three color images.

    Here's the paragraph from JS Friedman's 'History of Color Photography'... (page 145, available on Google books)

    "There is one field, however, that appears to be ideally suited for the screen plate. This is the use of a screened bipack in which the front element is a screen plate which registers two of the primaries, and the rear element registers the third. This procedure was first disclosed by Ives. The screen units in the front element were colored yellow and magenta, and these were coated with an emulsion sensitive only to the blue & green primaries. The blue densities would be registered only behind the magenta elements, while the green densities would register only behind the yellow lines. By the use of filters, it therefore becomes possible to copy the images behind these lines upon separate plates. Both the yellow and the magenta lines transmit the red rays w/ great efficiency. Since the front element is completely insensitive to this section of the spectrum, it will register only upon the rear element, and in the form of a continuous tone negative."

    Ok, so the difference would be that a bipack would be unncessary, as we'd theoretically have a camera capable of holding two plates/films. This would greatly simplify things.

    The logical application would be to make this two-color screen-plate and to place orthochromatic film behind it. This would go in one of the holders. From this you'd make your blue & green separations. The typical drawbacks of a screen plate (visible "grain", inability to enlarge much) would be greatly diminished as it only has 2 colors as opposed to 3. Therefore it would be higher resolution than all other screen plates.

    Then in your other film holder you'd have panchromatic film with a typical (29 or 25) red sep. filter.

    Since the red separation would be continuous and your screen-plate finer than ever, the overall fidelity would be far and away better than what we are used to with "screen-plate" photography.

    Once you obtained a well balanced screen plate, matching its sensitivity to the red sep. would be merely a matter of placing neutral density where it's needed.

    So, the concerns as I can see them would be.... is commercially available orthochromatic film the right sensitivity to be used for this kind of separation? And of course, making the screen-plate; but using a printer on transparency paper would certainly be easy, plus the integrity of the dyes used would be inconsequential, that is, they don't have to be "archival" really, since you could make your separations soon after, and then if the screen-plate faded over time it wouldn't really matter.

    Just something to put in your pipe and smoke....
    If you are the big tree, we are the small axe

  2. #22

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    This site probably has some of the best pictures of the Curtis, Bermpohl and Devon one shot cameras.
    http://www.vintagephoto.tv/index.shtml
    Check through the contents index and you will find more information on the various one shot cameras and colour separation information and a link to Yahoo where there is a discussion group on the history of colour photography.

    Gord

  3. #23
    holmburgers's Avatar
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    Cool, thanks for the link
    If you are the big tree, we are the small axe

  4. #24
    holmburgers's Avatar
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    If you are the big tree, we are the small axe

  5. #25
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    Quote Originally Posted by holmburgers View Post
    Good find!

    I had an active search going on for a while, and every time I found one it cost an arm and a leg.

    I still haven't abandon the idea of making one.
    Michael Batchelor
    Industrial Informatics, Inc.
    www.industrialinformatics.com

    The camera catches light. The photographer catches life.

  6. #26
    holmburgers's Avatar
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    Heck ya!

    I wonder how difficult it would be to do. Obviously the machining would have to be exceptionally good, but other than that, it's just a big box, right?

    If you made some that were good, I bet you could sell them at a reasonable rate. $5k?
    If you are the big tree, we are the small axe

  7. #27
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    Quote Originally Posted by holmburgers View Post
    Heck ya!

    I wonder how difficult it would be to do. Obviously the machining would have to be exceptionally good, but other than that, it's just a big box, right?

    If you made some that were good, I bet you could sell them at a reasonable rate. $5k?
    I don't thank it needs to be all that tight unless one really were trying to sell them as a commercial product.


    My thoughts were that you could make the beam splitters and film holders fit with a small screw adjustment so you could adjust the parallels and perpendiculars by trial and error.

    That makes it one of a kind instead of a mass production item. But its a start.

    Now, if I could clone myself I'd have time.
    Michael Batchelor
    Industrial Informatics, Inc.
    www.industrialinformatics.com

    The camera catches light. The photographer catches life.

  8. #28
    holmburgers's Avatar
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    As per cloning... we have the technology. But you'd be in charge of raising yourself up to, oh, whaddyou think?, 14 or so, before you could start buildling stuff. That's 14 years of maintaining the cellar, making sure it puts the lotion on the skin, etc... you don't want to do that!

    Ok, back to reality (that was creepy)...

    I think that these Curtis and Devin one-shots used half-silvered mirrors, but I know you're set on the beam splitter idea and that indeed could be a great route to take. I've just read numerous accounts in old books about how tight the tolerances need to be to ensure that the 3 negatives are in the identical plane of focus.
    If you are the big tree, we are the small axe

  9. #29
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    Quote Originally Posted by holmburgers View Post
    ...I think that these Curtis and Devin one-shots used half-silvered mirrors, but I know you're set on the beam splitter idea and that indeed could be a great route to take....
    That's all a beam splitter is, a half silvered mirror. Take a look at the Edmund's Scientific stuff.

    Quote Originally Posted by holmburgers View Post
    ... I've just read numerous accounts in old books about how tight the tolerances need to be to ensure that the 3 negatives are in the identical plane of focus.
    That's why I think building to tolerance is a tough plan. You have to build with the plan to shim as required, and do it empirically.

    I'm sure someone here knows how, but truth be told I'm certain I cannot calculate how the wavefront of the image changes with some parts going through one sheet of glass, and other parts going through two sheets. I know that affects the physical distance because of the transmission medium differences in the paths. But not in any way that I can predict.

    So, you build adjustment into the device, and you tweak!
    Michael Batchelor
    Industrial Informatics, Inc.
    www.industrialinformatics.com

    The camera catches light. The photographer catches life.

  10. #30
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    Ok... I must've been confuzzed on the beam splitter thing.. I seem to recall a discussion about beam splitters inside CRT TV's, but, regardless..

    That kind of calculation should be quite easy to do, and although I can't currently tell you how.. I guarantee we could figure it out.

    In fact, I believe that some designs used a "dummy" glass in the optical path to compensate for discrepancies of this sort.

    Imagine a one-shot 35mm or 120 camera! You could have 3 rolls of film in 1 camera. That would be awesome...
    If you are the big tree, we are the small axe

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