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Thread: Shutters

  1. #1

    Shutters

    So far there have been a few discussions of lenses, with some good leads on cheap glass. One hitch is what to do about a shutter. With glass instead of pinhole the exposure times get short enough that using a lens cap isn't very practical. I guess one can always locate a Speed Graphic and use the focal plane shutter with homebuilt lenses, but that limits the format a bit and a SG in good condition isn't all that cheap anyway. Using a shutter off an old folder can be a problem because of vignetting caused by the thickness and small bore of most folder shutters. That might be avoided by mounting the shutter between front and rear elements, just like on "real" lenses, but that creates mounting problems.

    Has anyone given much thought to homemade shutters?

  2. #2

    Shutters

    i have seen shutters rigged up from metal plates with a cut-out slot that briefly passes the aperture when dropped within a holder (guillotine-style). this was used on pinholes, and might be hard to calibrate the falling speed/slot size with a lens, but it could be one solution.

  3. #3

    Shutters

    Quote Originally Posted by moot
    So far there have been a few discussions of lenses, with some good leads on cheap glass. One hitch is what to do about a shutter. With glass instead of pinhole the exposure times get short enough that using a lens cap isn't very practical. I guess one can always locate a Speed Graphic and use the focal plane shutter with homebuilt lenses, but that limits the format a bit and a SG in good condition isn't all that cheap anyway. Using a shutter off an old folder can be a problem because of vignetting caused by the thickness and small bore of most folder shutters. That might be avoided by mounting the shutter between front and rear elements, just like on "real" lenses, but that creates mounting problems.

    Has anyone given much thought to homemade shutters?
    Well, there are always Packard shutters, made to be mounted in front or behind the lens. Most rotary shutters (as on box cameras) are mounted that way as well (kind have to be, with a single-element lens).

    And if you use slow enough material, too-short exposures are less of a problem. ISO 25 too fast? Try enlarging paper. Still too fast? Go to contact-speed paper (there are still a couple types available). *Still* too fast? There's always cyanotype, kallitype, salted paper, and other "alt processes", some of which have been used in camera either originally or recently. With these last, to be prepared to find your print requires a different focus than what you see in the ground glass; most lenses focus UV light a little shorter than visible....

    I've seen improvised shutters using an aperture cut in a matt board card, propelled by gravity or rubber bands, essentially a "guillotine" shutter. If you know what you're doing, you can cap-shutter under a second, also (though a half second seems about as short as is likely to be practical).

  4. #4

    Shutters

    Going back into the depths of an old sketch journal of mine...I think you can build a "guillotine" shutter from thin sheet metal or aircraft plywood. Spring loaded, either metal springs or rubber bands for starters. I see the shutter moving horizontally, rather than vertically, so acceleration caused by the falling mass wouldn't happen (you'll get a more consistent shutter speed).

    The moving shutter plate would have a variable-width slot, calibrated in fractions of a second. Even a crude spring-loaded sliding plate could have a really fast shutter speed with a thin enough slot.

    For calibration of the shutter positions, I've used an optical sensor (photodiode) from a VCR, with a oscilloscope to measure the resulting voltage pulse width. But there's other methods possible. I've heard of recording the sound of the shutter snapping, using a microphone into the computer as a .WAV file, then measuring the width of the sound pulse in fractions of seconds using audio editing software.

  5. #5

    Shutters

    Thanks for the input, guys. I haven't had much time today to think about your comments, but Joe got me thinking about a spring-driven guillotine with some sort of adjustable dashpot for controlling speed. In a previous life I used adjustable bleeds on pneumatic actuators to control the stroke speed, but I haven't played with dashpots. Anyone have any experience with them?

  6. #6

    Shutters

    I've only seen them in textbooks.

    I've thought about alot of hideous contraptions but not tried (m)any out.

    floppy disc shutter

    ball point pen as prime mover. Prestretch springs as far as possible & still fit back in the pen body. Two for different speed.

    Retractable keychain/id badge clip (does my description make sense?)

    elastic cord.

    elastic cord with 'parachute' spring cushion at stop. Physics profesor discouraged that, if it's not damped well, it could have ugly oscillations/vibrations.

    magnetic catch at stop.

    vibration before and after aperture is uncovered can be managed if materials don't resonate endlessly. (stuff like matboard won't 'ring' lke metal

  7. #7

    Shutters

    I have spent alot of time thinking on this problem and havent come up with anything like a usefull conclusion. In my own recent project I ended up hacking the lens out of an old twin lens reflex and using it as is.

    But recently I thought maybe I could pull the shutter mechanism out of an old polaroid and modify it. I think they are mechanically simple enough for that to be possible and sophisticated enough that some of the auto exposure stuff that they tend to do might be useable?

    Never actually tried it . Anyone else been down that route?

  8. #8

    Shutters

    imagemaker has hacked polaroid cameras to use auto exposure. do a search on his past posts and there may be something relevant. i don't know if he has ever relocated the whole shutter, but he would probably know what could or couldn't be done.

  9. #9

    Shutters

    Yes, taking the whole shutter assembly out of a Polaroid is both possible and practical, at least with the simpler models like the 210 I hacked. The connection to the body is only via the screws that hold the front board together, the wires that bring power from the battery (3 V or 4.5 V, depending on the model) and the fairly ordinary cable release from the release button on the body. Unsolder the power wires and lift the shutter off the cable, and it's all in your hand, completely self contained.

    What you *don't* get is the adjustment system for lighten-darken (a moveable, gradient filter in front of the light sensor). You do, however, get the flash synch, including the switch that locks the shutter speed for flash if the connected flash has the L-shaped bar next to the PC connector, all the timing circuitry, and the apertures (either on a rotating wheel or a sliding plate, depending on the version).

    The Polaroid shutter, as implemented from about 1961 into the late 1970s on these pack-film folders (and probably also on the non-folding plastic pack film cameras) can expose from 1/200 to about 8 or 10 seconds, depending soleley on the light falling on the sensor; film speed adjustment was by a combination of apertures for the lens and filters for the sensor. The shutter tension is adjustable on most versions (the spring can be set in different notches); this adjusts the high speed, and on the better models, there are electronic adjustments for overall exposure and linearity, also.

    I might also suggest, a simple rotary shutter similar to those in 1930s to 1950s box cameras (or a modern Holga) could be made by a home hobbyist with a drill, snips, round-nose pliers, plus some brass sheet, music wire, and a few screws and nuts or rivets. A *seriously* simple one only needs a sector of metal with a hole in it to match the aperture, a lever to turn it on a pivot, and a spring set up as an over-center (so the sector will "sit" at either end of its travel under spring tension) to give the earliest type of simple shutter, which exposes on both push and pull stroke. Shutter speed is set by spring tension, sector mass, and hole width.

  10. #10

    Shutters

    You could buy a holga shutter mechanism from Holgamods for 9.99 plus 4.50 shipping, or pay 19.99 + shipping for a holga from B and H.

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