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Thread: Shutters

  1. #11

    Shutters

    Quote Originally Posted by Willscraig
    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.
    if you're gonna do that you could also consider canabalising any one of a number of old cameras with similar shutters like an old box camera etc... and afterwards, you might even want to turn the camera body into a pinhole?

    I also like diana type cameras and I've sometimes found them for sale cheap because the shutter is "broken" but it's almost always something you can fix with cleaning and lubrication, so even a "broken" shutter migt be worth grabbing if it's cheap enough [but please don't kill the original dianas because they resell for too much!!!]

  2. #12

    Shutters

    To foolow on from JoeVanCleave's comments about shutters, you can find a shutter tester at this url
    <http://www.davidrichert.com/sound_card_shutter_tester.htm>.
    I still have a similar design I made a few years ago and have found it simple to use in conjunction with my sound card. My main use was/is estimationg the actual speeds of shutters on some old cameras I have.
    Still doesn't solve the problem of designing your own shutter tho'.

  3. #13

    Shutters

    Interestingly enough, I have been disassembling a Polaroid EE100 in hopes of using it tomorrow (WWPD 2006), but my attempts to get an exposure have been unsuccessful. I have a series of images I call "Lilies by Night" but that's not what I was going for.

    The last exposure was 50 seconds and still as dark as can be. The pinhole diameter is whatever you get with a straight pin, fashioned from a piece of brass shim mounted on card stock. Looks clean. I have also put a pinhole (larger diameter) over the light sensor but I think I am entering Rube Goldberg territory there.

    The film is Fuji 100 instant film, not Polaroid stuff.

    I was thinking I would see *something* at a minute, since 15 seconds didn't reveal much. The 50 seconds was what the occluded light sensor called for. And it was raining persistently enough, I didn't try for the extra 10 seconds.

    I only have 2 exposures left, so I may wait til tomorrow in hopes of a brainwave. I'm resigned to manual exposures, I think. The light sensor business is fraught with complications I don't need. I'll just knock the shutter out, I guess. Seems silly to keep it, given it won't work without batteries.

  4. #14

    Shutters

    You're probably around f/300+ with that pinhole, if it's at the original aperture location, Paul. My AutoPin 210 has an aperture about 1 mm diameter over the CdS cell, and then two stops of neutral density over that, as well as the original Polaroid gradient filter that produces the lighten/darken function -- but my camera is dedicated to shoot Type 667, ISO 3000, only. With f/320 on ISO 100, in "stormy" conditions (five stops off Sunny 16), you'd be looking for an exposure, exclusive of reciprocity failure, of around 128 seconds. Add reciprocity correction (Polaroid films require it for exposures beyond 1/10, approximately, and it's worse than the 3 for 2 that Tri-X and most other conventional films like) and you'd be looking for exposures in excess of an hour (possibly multiple hours -- Polaroid's reciprocity charts don't go that far) with that film and that light.

    If you load up with Type 667 or the Fuji version of 3000 speed, you should be able to get sunshine exposures of around 1/4 to 1/2 second, and even the stormy conditions you've had today would give you exposures (with reciprocity correction) of under a minute. And in Chicago, you *ought* to be able to find a photo store that sells 667 even on a Sunday...

  5. #15

    Shutters

    Eeep! 128 seconds?! Good thing I got the shutter release working: I'll need the locking one for that.

    And yes, it is at the end of the bellows, replacing the surprisingly good but now useless plastic lens components.

    It bids to be a fair day tomorrow, so I should be in good shape for the slower speed film. I have my 120 pinholer ready to go, so all is not lost.

    Thanks for the info, and looking forward to contributing *something* tomorrow.

  6. #16

    Shutters

    Quote Originally Posted by moot
    . . . 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?
    The Compound shutter found on some older lenses uses a pneumatic cylinder. So do some even earlier shutters. You might get construction ideas from them. Better yet, find one with one of the good classic lenses.

  7. #17

    Shutters

    Paul, that 128 seconds was before applying reciprocity correction. Using 3 for 2 correction starting from 1/10, the corrected figure would be approximately 2 hours and 20 minutes.

    In full "Sunny 16" conditions, at ISO 100 and around f/320, you'd be five stops better, or about 4 seconds before correction and around 35 seconds after -- which is quite reasonable if you have a tripod socket and cable release. Same conditions on ISO 3000, BTW, would give about 1/8 to 1/4 second, requiring at most 1/2 stop correction (so under 1/2 even with correction).

    I'm calculating the reciprocity corrections, BTW, by taking the log base 2 of 10 times the exposure time (to start correction from 1/10), then raising 3 to that power and dividing the result by 10 to get back to seconds; that's the same as tripling time for each stop instead of doubling, which works very well for almost all conventional negative films and metered exposures up to several minutes (which work out to multiple hours after correction). Helps to have a scientific calculator. I use this method (but starting from 1 second for most films) for all my manually exposed pinhole shots, and my negatives are always reasonably well exposed even if there are serious other problems. And working from one second, I can do this in my head...

  8. #18

    Shutters

    Yeah, I grokked that after re-reading.

    I just took another shot w/ 1 minute of exposure (even with the light sensor covered, I had to hold the shutter down 3 times!) and I'm close. Perhaps w/in a stop. My opportunities to work with that subject have vanished: a little basketball workout claimed the only two lilies that were in bloom ;-(

    The pinhole is pretty big as it turns out: compared to my laser-drilled one, I'd guess it's 1.5 to 2 times larger. I'd put it at under 200, based on nothing than intuition.

    If I had any confidence in the Luna-Pro I just picked up, I could use that, but I find my guesses are closer so far.

    Thanks again for the tutorial. Much to learn and much to try.

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