A Faster Leaf Shutter?

Discussion in 'Camera Building, Repairs & Modification' started by bvy, Jun 1, 2012.

  1. bvy

    bvy Subscriber

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    I have several "lo-fi" cameras that employ a simple, single blade leaf shutter, the likes of which can be seen here.
    500px-Leaf_shutter.svg.png
    Wikipedia link

    What I'd like is to modify some of these to have a really fast shutter. I realize I'm not going to get 1/1000 or even 1/500 out of it, but something in the neighborhood of 1/125 to 1/250 would be wonderful. (My Vivitar Ultra Wide & Slim, for instance, clocks at a blurry 1/80 and usually overexposes). Given the limitations of its simple design, how fast can these shutters get (in theory or in practice)?

    And, in general, what are some strategies for speeding up such a shutter? The most obvious approach seems to be to add tension to the springs (the one that cocks the shutter and the one returns the blade to its closed position) so that the blade pops out of and back into position more quickly. I've done this with mixed results. Is there a better or more novel way?

    Thanks.
     
  2. E. von Hoegh

    E. von Hoegh Member

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    You're pretty much stuck with low speeds with that design. It isn't suitable for high speeds, this is the reason leaf shutters such as the Copal are designed as they are. Your shutter is the same design box Brownies were using over 100 years ago.
     
  3. Steve Smith

    Steve Smith Subscriber

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    If it had a wider moving leaf with a hole in it, it would give you an effective faster speed without actually moving faster. Instead of uncovering the lens it would just pass an aperture over it.


    Steve.
     
  4. E. von Hoegh

    E. von Hoegh Member

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    A sector shutter. It seems his shutter moves the leaf away, then back. He'd have to modify it with a new blade, and then solve the problem of cocking it.
     
  5. Ken Nadvornick

    Ken Nadvornick Subscriber

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    In effect, this is what happens with the little rotary shutter in a Kodak Hawkeye Brownie. A cutout hole in a larger leaf, where larger in this case means a rotating partial disk. I simply used black photo tape to mask the cutout to a smaller size. Trial and error with a shutter speed tester guided the degree of masking required to achieve the speed I wanted.

    Ken
     
  6. ic-racer

    ic-racer Member

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    Am I missing something? Isn't that the point of a "lo-fi" camera? :smile:

    Did you try cleaning the shutter? Maybe it was faster when new.
     
  7. Dismayed

    Dismayed Member

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    Flash several stops above ambient will create fast 'effective' shutter speeds. Pry it with a Buff Einstein mono light.
     
  8. polyglot

    polyglot Member

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    I came here to suggest what Steve did. You can replace the blade with a wider one; it will possibly move slower if you make it heavier but you can reduce the total exposure by cutting a narrow slot in it that passes over the hole. If you can't prevent the shutter blade from returning you will get a kind of double exposure though; one swipe of the slot each way. If nothing else, the results would look very funky with fast-moving subjects like propellers!
     
  9. Dan Fromm

    Dan Fromm Member

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    Um, Polyglot, would you by any chance have a bakelite-bodied Brownie Hawkeye? I ask because that was my first camera and until I learned how the shutter worked I got unexpected and sometimes surprising double exposures with it.

    This because pushing the shutter release lever down fired the shutter and pulling it up also fired the shutter. I think the wikipidia entry bvy directed to us misrepresents how those shutters function.

    More seriously, the simple shutters being discussed are a kind of guillotine shutter. Sector shutters have been used in a few still cameras (Univex Mercury, Olympus Pen F) but are nearly the norm for cine cameras. The Agiflite, an aerial camera that shot 6x6 on 70 mm film and is essentially a cine camera with a low framing rate, has a rotary sector shutter whose top speed is 1/2000.
     
  10. polyglot

    polyglot Member

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    I don't have any sector- or guillotine-shutter cameras, though I've considered building one so that I can use an Aero Ektar.
     
  11. bvy

    bvy Subscriber

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    Thanks for the responses. I wasn't looking for huge gains and couldn't accept that I was stuck with 1/80 for the camera I'm currently working on (the Vivitar Ultra Wide & Slim) -- especially when the specs claim a 1/125 shutter speed. Also, I have a reclaimed disposable camera, same shutter design, that clocks between 1/125 and 1/160. So I'm sure that some modest gains are possible.

    I did more exploratory surgery this weekend. Unlike the diagram, this camera uses a regular coil spring to return the shutter blade. I doubled it up around the lug and attached both ends to the shutter blade. Also, I added a tiny piece of balsa to shorten the path that the blade travels. I tested extensively. The bad news is I now have a variable speed shutter. The good news is it varies between about 1/100 and 1/125 -- up from a constant 1/80. I only see this as a short term fix however.
     
  12. Denverdad

    Denverdad Subscriber

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    First of all, I think it’s great that you are trying to modify your camera to get what you want out of it! Tinkering with cameras is something of a hobby of mine, especially old medium format viewfinder cameras from the '40's and '50's. Some of these are distinctly lo-fi and others not so much; but typically they sport simple single-speed shutters similar to yours. I can say that in my experience there is almost always SOME way to increase the shutter speed, at least to within a factor of two or so.

    In the case of a swinging paddle shutter like yours, the first thing I would suggest is to make sure the mechanism is as clean as possible, especially between the paddle itself and what it is sliding on. Any dirt or dust in there will slow it down, as will (perhaps counter-intuitively) any oil or grease.

    Other than that, spring modifications are the most obvious thing to do. For a tension spring like you have, shortening the length is the basic way to increase tension and thus speed things up. Rather than doubling the spring over though, I think you might have better luck if you simply cut the spring to a shorter length, then bent and reformed the cut end to match what was there before so it can hold onto whatever it is connected to. You want to make the spring motion as smooth as possible, trying to avoid coils sliding over any surface, or having coils catching on eachother. Admittedly, cutting and bending springs tends to be kind of fiddly work. But if you have some needle nose pliers and a little patience, it is really not that bad. I do it all the time! :smile:

    As others have mentioned, if the moving disk or blade (or whatever the shutter uses) has a slot or other opening in it that lets the light through, one of the easiest ways to increase the speed is to mask that opening to a shorter length. But I don’t think that’s what you have, so probably a moot suggestion.

    Limiting the range of motion is another good idea, like you did with the piece of balsa. I hadn't thought of that one!

    A final technique I can think of is to lighten the moving parts where you can. If you can remove the blade, you might be able to drill holes or clip edges off of the paddle to lighten it, provided that the cuts do not let any extra light through the hole as the blade moves. You could also sand the surface of the paddle to remove material. Granted, these are pretty desperate measures and honestly, I haven't tried them. But in theory it should work!

    Good luck!

    Jeff
     
  13. bvy

    bvy Subscriber

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    Thanks for the thoughtful response, Denverdad. Makes sense, especially about doubling over the spring the way I did. Still experimenting with this...