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  1. #1
    Mustafa Umut Sarac's Avatar
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    Slit Scan Strip Street Camera

    I am thinking to construct a very compact slit scan strip camera for street photography . I think I will use 220 film and a 2 cms high, 3 strips on single film roll.
    Lens will be a slit and it will only 2 cms long , by the way I will be able to record more than 3 meters long strip on the street.
    Well there is technical problems :
    What might be the distance between two walls of the slit ?
    What might be the film to slit distance ?
    I am dreaming - because I have no idea about the design dimensions - a hand cranked roll and a feeder roll , a 2 cms slit on a sliding bar which will carry the slit on to the film for 3 different strips .
    I think key element is the film flow speed.
    It will record the movements continiously and may be this is a movie camera .

    Best ,

    Mustafa Umut Sarac

    Istanbul

  2. #2
    polyglot's Avatar
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    You need a lens, mounted the appropriate distance from the film. Slit goes behind the lens, probably right up next to the film plane. Film must be fed through it at a rate that exactly matches the rate at which the lens is rotating (which is a function of the magnification of what the lens is imaging), otherwise you will get smearing. Width of the slit and film transport rate will define how much exposure you get.

    I would suggest building a non-rotating camera first as it will be much much easier to get right. You can still build a slit shutter for such a camera of course - some old LF cameras had a slit shutter. As before, slit width and its speed with respect to the film will define your exposure. You can get some cool effects with a camera like this when things in the scene are moving - they get expanded, compressed or sheared depending on their direction of travel.

  3. #3
    Mustafa Umut Sarac's Avatar
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    Polyglot , What do you mean with smearing ?

  4. #4
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    If you're talking about a stationary lens, stationary film and having a slit move across the film plane, there is no issue with smearing. It's a fairly simple camera with not a lot to go wrong, but you must have a lens with enough coverage to illuminate the whole frame (strip of film) at once.

    However, you're talking about recording strips that are metres long, which implies that the film is moving through the camera and the camera is presumably rotating so that each part of the film records a different part of the image. These are known as rotating or pivoting panorama cameras, of which there are a few kinds in existence like the Cirkut, Horizont and more. If you build such a thing, you need to make sure that the rate at which the lens rotates past the scene exactly matches the rate at which the film slides past the slit otherwise your image will be horizontally blurred by the width of the slit. The ratio of rates depends on the focal length and magnification of the lens.

  5. #5

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    It sounds like what you want to look at is what is classically called a "photofinish camera". These were/are used to photofinish races. No, they don't just use a camera like the ones we use. The lens is stationary, the slit is next to the film, and the film moves at the rate the subject is expected to move at. Take a look at this RIT page. It should get you started. I've always wanted to give it a try, but so far have resisted my urges.

    http://people.rit.edu/andpph/text-photofinish-race.html

    Denis K



 

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