Switch to English Language Passer en langue française Omschakelen naar Nederlandse Taal Wechseln Sie zu deutschen Sprache Passa alla lingua italiana
Members: 70,499   Posts: 1,543,159   Online: 1088
      
Page 2 of 6 FirstFirst 123456 LastLast
Results 11 to 20 of 58
  1. #11
    michaelbsc's Avatar
    Join Date
    Dec 2007
    Location
    South Carolina
    Shooter
    Multi Format
    Posts
    2,106
    Images
    5
    Quote Originally Posted by holmburgers View Post
    Howdy everyone,

    I've been intrigued lately by one-shot cameras; you know, the ones that took 3 separation negatives at once. It's hard to find any good resources online, does anybody have some links or something?

    I'd like to see the high end models, as well as more consumer oriented ones (though I doubt many consumers used them).

    Cheers
    I've been toying with the mechanics of trying to build one, and it's not trivial. Getting a Phillips prism that will work is the hard part to do a professional job of it. I have yet to locate an old '60s TV camera to cannibalize. Modern Phillips prisms are minuscule.

    However, searching prisms unsuccessfully at Edmund Scientific I did hit on the idea of trying to do it subtractively rather than additively. This way you only need two images.

    You can easily get a plate beam splitter that's fairly large to split the incident beam. The transmitted beam will be reduced by slightly more than one f-stop, and the reflected beam will be approximately the same but oriented improperly because of the reflection. You'd need a front surface mirror to reverse the orientation of the reflected beam.

    Several email exchanges with the Edmund Optical support team agreed that the beam splitter shouldn't affect the optical quality of the image produced by the lens in either the transmitted or reflected image. So long as the light paths are equal you'll get two images focused on the targets, each with slightly less than half the light of the original incident beam. (There is some loss in the beam splitter, but not a lot if it's professional quality optical gear.)

    Plus you'd need the proper filters to make your negatives carry the right information.

    And finally the reproduced color rendition isn't spectacular, just pretty good. This is why Technicolor's three color system blew away the two color systems that preceded it. Three color additive is capable of rendering true colors across the spectrum. Two color is a trick to get us to perceive missing colors that works because of how our eye/brain system is constructed.

    Making a two color system at home isn't 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.

    Of course, you could always take three images with filters, but that's not what the thread is about.
    Michael Batchelor
    Industrial Informatics, Inc.
    www.industrialinformatics.com

    The camera catches light. The photographer catches life.

  2. #12
    holmburgers's Avatar
    Join Date
    Aug 2009
    Location
    Rochester NY (native KS)
    Shooter
    Multi Format
    Posts
    4,420
    Images
    2
    Wow, indeed that is quite the undertaking. The necessary precision boggles the mind, especially with a 3 color set up.

    I wasn't familiar with the Philips Prism, by name at least. This is interesting... http://www.alt-vision.com/color_prisms_tech_data.htm

    So I admit that I'm not up on the "latest" in tri-color separation (*cough *cough, when would that have been, 1951? ) but what about reflectors that can selectively reflect colors? Mirrors were coated by means of sputter deposition techniques to produce only reflections of given wavelenghts. This would eliminate the need for filters.

    In the book mentioned in my OP this was discussed, but he introduced it more as the "standard" by which all other systems will be judged, saying that this is theoretically possible. So IDK about logistics.

    Another question; do the separation filters all possess the same filter factor, and if not, how does one match exposures? ND? Only a consideration with a one-shot obvioulsy.
    If you are the big tree, we are the small axe

  3. #13

    Join Date
    Jun 2003
    Location
    Portland, Oregon
    Posts
    1,337
    The red filter tends to pass a bit more light than the others. I seem to remember the need to sandwich a bit of cyan filtration with the red to balance out the transmission, in effect creating a bit of neutral density. I think it was about 1/3 stop. You'll need better research than my memory, however.

    Peter Gomena

  4. #14
    michaelbsc's Avatar
    Join Date
    Dec 2007
    Location
    South Carolina
    Shooter
    Multi Format
    Posts
    2,106
    Images
    5
    Here's little more information than I had the other night. Not much mind you.

    http://www.widescreenmuseum.com/oldc...ubtractive.htm

    Look down near the very bottom of the page above for the two-color subtractive information. This is the page that got me thinking about using a plate beam splitter and a front surface mirror. It is boatloads easier than finding or fabricating a Phillips prism.

    I did toy with the idea that you could just use several beam splitters to get your three images, but that's a lot of loss in the system. Basically you'd loose at minimum 2 stops if they system is perfect. And the beam splitters farther down the chain have to get pretty big or you have to stick with small negatives. When I said earlier that a plate beam splitter was affordable I didn't mean 8x10! The Phillips prism avoids those losses.

    Another link for two color:

    http://www.widescreenmuseum.com/oldcolor/subtract.htm

    Sorry there's no hard core data here. I guess we have to rediscover it and make it up for ourselves.
    Michael Batchelor
    Industrial Informatics, Inc.
    www.industrialinformatics.com

    The camera catches light. The photographer catches life.

  5. #15
    holmburgers's Avatar
    Join Date
    Aug 2009
    Location
    Rochester NY (native KS)
    Shooter
    Multi Format
    Posts
    4,420
    Images
    2
    Michael, kudos for the links; very cool.

    You know, it's almost more interesting to see a 2-color approach because afterall, we're so used to seeing beautiful, 3-color reproductions that nearly mimick reality. It's more interesting/profound to see something that's slightly different from reality. I'm on your 2-color bandwagon!

    Hey, check out this book and go to Chapter 5. It's the Friedman book I've been alluding to. He basically outlines all approaches that have been taken for color-separation cameras.

    You're sure to find some new, novel idea that perhaps hadn't occured to you before and might make your task easier. It's what I would describe as "very thorough".

    As for the two-color requirements, are you still searching for the appropriate filters to do it? I'm sure this information is in some book somewhere, I'll try to do some searching.
    Last edited by holmburgers; 07-30-2010 at 11:47 AM. Click to view previous post history.
    If you are the big tree, we are the small axe

  6. #16
    2F/2F's Avatar
    Join Date
    Apr 2008
    Location
    Los Angeles, CA
    Shooter
    Multi Format
    Posts
    8,008
    Images
    4
    The big benefit of the one shot camera is that things do not have to be still to photograph them and get a "normal" picture. If you do three separate exposures, any movement between shots will result in some pretty psychedelic effects where the movement occurred.
    2F/2F

    "Truth and love are my law and worship. Form and conscience are my manifestation and guide. Nature and peace are my shelter and companions. Order is my attitude. Beauty and perfection are my attack."

    - Rob Tyner (1944 - 1991)

  7. #17
    BetterSense's Avatar
    Join Date
    Aug 2008
    Location
    North Carolina
    Shooter
    35mm
    Posts
    2,863
    I did toy with the idea that you could just use several beam splitters to get your three images,
    If you are talking about partially-silvered mirrors, I'm not sure if it would work as well as you hope. Usually optical mirrors are silvered on the front surface, so that the light isn't refracted twice from traveling through the glass on the front of a conventional mirror. If you used a partially silvered mirror, the light that bounced off the front would go one way, and that that went through the mirror would go another way.

    This might be fine depending on what your criteria are for alignment. It seems to me that if I were doing it, I would just give up on trying to get the 3 negatives exposed so the images were perfectly aligned when you stacked them up for printing. You would need a lot of precision to do that. But if you can resign yourself to visually lining up the negatives on a light box, then your camera just has to have the same magnification between the 3 negatives, and they can be misaligned by quite a bit (whole mm) without it being a problem.
    f/22 and be there.

  8. #18
    michaelbsc's Avatar
    Join Date
    Dec 2007
    Location
    South Carolina
    Shooter
    Multi Format
    Posts
    2,106
    Images
    5
    Quote Originally Posted by BetterSense View Post
    If you are talking about partially-silvered mirrors, I'm not sure if it would work as well as you hope. .... But if you can resign yourself to visually lining up the negatives on a light box, then your camera just has to have the same magnification between the 3 negatives, and they can be misaligned by quite a bit (whole mm) without it being a problem.
    I don't see that image alignment is terribly hard. Tedious for certain, and it would probably take a while to get it right. But I don't see it as intrinsically hard.

    As for magnification, if you're shooting all three negatives through the same lens simultaneously, then this cannot be a problem unless you have some other lensing elements in one of the paths. After all, if you've got the image focused on three GGs at the same place, then all three signal paths must necessarily be the same, hence the magnification must be the same.

    The biggest problem with using beam splitters to get three color separation in my mind is loss of light in the process. Each pass will give you a one stop decrease, and then the filter factors have to come into play. Even if you start at f/11, you're going to wind up doing no better than f/32 by the time you get to the film plane. And maybe even worse if you've got to introduce a bunch of neutral density in some filters to get them all to match. (OK, Ok, to the purist it isn't really smaller diameter f-stops, but signal attenuation along the transmission pathway. But when calculating exposure I, and probably most of us, think in f-stops.)

    The Phillips prism is the Cadillac method to do the separation, but so far I haven't found any unused Phillips prisms laying around in my junk stash. If anybody has a spare one let me know!!

    (I even thought of cutting up a bunch of acrylic sheets and making a Phillips prism out of water chambers, but I don't know enough about the physics of light to figure out the dimensions based on the differences between glass and acrylic/water. I know it's different, but I don't know how to correct for it.)

    Hence my searches for the two color method. There's far less attenuation in the signal path with only a single split. So what if you do two-color and it isn't true color; sometimes you gotta compromise. It is just a hobby, after all.

    And I did track down the filter colors at one point, but I've lost that info.

    MB
    Michael Batchelor
    Industrial Informatics, Inc.
    www.industrialinformatics.com

    The camera catches light. The photographer catches life.

  9. #19
    2F/2F's Avatar
    Join Date
    Apr 2008
    Location
    Los Angeles, CA
    Shooter
    Multi Format
    Posts
    8,008
    Images
    4
    If contacting a user of these cameras "back in the day" is of any interest to you, Richard C. Miller is still alive, here in Los Angeles, at age 98 (http://www.richardcmiller.com/).

    His film holders (5x7) had built-in filters. (I know this because I have seen them in person.)

    He used a National Lerochrome camera like this one (a measly 3x4, though it is very neat that it is a tungsten model): http://www.collectiblecameras.com/pr...cat=350&page=1. It is now owned by his assistant.
    Last edited by 2F/2F; 07-30-2010 at 03:10 PM. Click to view previous post history.
    2F/2F

    "Truth and love are my law and worship. Form and conscience are my manifestation and guide. Nature and peace are my shelter and companions. Order is my attitude. Beauty and perfection are my attack."

    - Rob Tyner (1944 - 1991)

  10. #20
    holmburgers's Avatar
    Join Date
    Aug 2009
    Location
    Rochester NY (native KS)
    Shooter
    Multi Format
    Posts
    4,420
    Images
    2
    That Lerochrome model is a beauty!

    As for equalizing exposures on the film end, it'd be interesting to experiment with different film speeds for each color. This introduces problems with contrast though, but perhaps a system of development could be worked out to minimize the effects. But as I understand it, keeping the same contrast is pretty crucial for accurate color, for obvious reasons.
    If you are the big tree, we are the small axe

Page 2 of 6 FirstFirst 123456 LastLast


 

APUG PARTNERS EQUALLY FUNDING OUR COMMUNITY:



Contact Us  |  Support Us!  |  Advertise  |  Site Terms  |  Archive  —   Search  |  Mobile Device Access  |  RSS  |  Facebook  |  Linkedin