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  1. #1
    narsuitus's Avatar
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    Sync terminology questions

    Are these sync terms and their definitions accurate?

    · Fast Sync—synchronizing a flash to fire with a fast shutter speed (1/60 second or faster)

    · Slow Sync—synchronizing a flash to fire with a slow shutter speed (1/30 second or slower)

    · Dragging the Shutter—synchronizing a flash to fire with a slow shutter speed (1/30 second or slower)

    · Front Curtain Sync—when using a camera with a focal plane shutter, synchronizing the flash to fire immediately after the camera shutter first opens.

    · Rear Curtain Sync—when using a camera with a focal plane shutter, synchronizing the flash to fire just before the camera shutter closes.

    Are these terms also accurate for a camera that has a leaf shutter or no shutter?

    Are these terms accurate for the times when the camera performs the sync function as well as for the times when the photographer manually performs the sync function?

    Are there other related sync terms?

    Other than balancing the ambient light in a scene with the light output of a flash, are there other uses for synchronizing a flash to fire with slow shutter speeds?

  2. #2
    rbarker's Avatar
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    Are these terms also accurate for a camera that has a leaf shutter or no shutter?

    A leaf shutter will sync at all speeds, so most of the terms don't really apply.

    Dragging the shutter really relates to allowing more ambient light contribution to the total exposure. As such, it could be anything slower than the maximum sync speed.

    Are these terms accurate for the times when the camera performs the sync function as well as for the times when the photographer manually performs the sync function?

    Nope.

    Are there other related sync terms?

    Although most modern cameras and lenses now only perform X sync (0 delay) for electronic flash, don't forget M sync (slight delay for flash bulbs) available on some older lenses.

    If you turn off the flash, and then fire the residual charge, would that be called "draining the sync"?

    Other than balancing the ambient light in a scene with the light output of a flash, are there other uses for synchronizing a flash to fire with slow shutter speeds?

    Sure. In part, the balance between flash and ambient light depends on which you want to be the primary light source. You might prefer, for example, for the flash to provide only fill. Using a slower shutter speed might also be used to introduce some motion blur into the image. One might also use a slow shutter speed in conjunction with flash bulbs, if the camera or shutter doesn't have M sync.
    [COLOR=SlateGray]"You can't depend on your eyes if your imagination is out of focus." -Mark Twain[/COLOR]

    Ralph Barker
    Rio Rancho, NM

  3. #3
    Charles Webb's Avatar
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    M sync = A 20 milisecond delay in tripping the flash to allow the shutter to reach it's maxium apperature before the bulb reaches it's brightest point..

    X sync = Instant tripping of the strobe as the shutter reaches it's maxium apperature.

    The flash bulb needs the 20 milliseconds to head start it's flash (burn) so that the brightest point in the flash syncs with the shutter reaching the point it can allow the maximum amount of light to pass through it.

    Charlie....................

  4. #4
    Helen B's Avatar
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    The 20 ms delay with M sync is/was for medium speed bulbs, hence the 'M'. There were also F, fast and S, slow bulbs with 5 ms and 30 ms delays to peak respectively. F bulbs could be used with X sync at slow-ish speeds. M bulbs can be used with X sync at slow speeds - in fact that is the most efficient way to use them (ie the way to get the most usable light from them). Some cameras (eg some Zorki 4 and all Zorki 5 I think) have adjustable delays and a version of the Rapax Synchromatic shutter has X, F and M settings.

    Best,
    Helen

  5. #5
    David H. Bebbington's Avatar
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    Quote Originally Posted by Charles Webb
    M sync = A 20 milisecond delay in tripping the flash to allow the shutter to reach it's maxium apperature before the bulb reaches it's brightest point..

    X sync = Instant tripping of the strobe as the shutter reaches it's maxium apperature.

    The flash bulb needs the 20 milliseconds to head start it's flash (burn) so that the brightest point in the flash syncs with the shutter reaching the point it can allow the maximum amount of light to pass through it.

    Charlie....................
    Just to be clear (although very few APUGers will be using M class bulbs in practice):
    M sync = A 20 millisecond delay in FIRING THE SHUTTER to allow the bulb to reach its brightest point when the shutter is fully open.

    This will become clear if you have an opportunity to work with (or at least look at) a camera with infinitely variable flash sync such as a Leica If, IIf or IIIf. An interesting way to get the effect of "second curtain sync" with a LEAF shutter would be to find an old-style Kalart external synchroniser. There was one model with switchable X/M sync but also if I recall an earlier one which had some kind of screw-threaded sleeve and was thus fully adjustable.

  6. #6
    Donald Qualls's Avatar
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    Quote Originally Posted by Helen B
    The 20 ms delay with M sync is/was for medium speed bulbs, hence the 'M'. There were also F, fast and S, slow bulbs with 5 ms and 30 ms delays to peak respectively. F bulbs could be used with X sync at slow-ish speeds. M bulbs can be used with X sync at slow speeds - in fact that is the most efficient way to use them (ie the way to get the most usable light from them). Some cameras (eg some Zorki 4 and all Zorki 5 I think) have adjustable delays and a version of the Rapax Synchromatic shutter has X, F and M settings.

    Best,
    Helen
    Actually, a couple of the more common bulbs still to be found as NOS or in old photographer's caches are a hybrid MF type, with a 15 ms ignition time instead of the 5 of F or the 20 of M. This includes AG-1 and AG-3 bulbs, as well as M2, but M3, M5, and all bayonet bulbs (other than the gas-filled F type) are M type bulbs (unless they're FP bulbs with their 1/8 second burn time to cover the entire travel of a Speed Graphic's focal plane shutter).
    Photography has always fascinated me -- as a child, simply for the magic of capturing an image onto glossy paper with a little box, but as an adult because of the unique juxtaposition of science and art -- the physics of optics, the mechanics of the camera, the chemistry of film and developer, alongside the art in seeing, composing, exposing, processing and printing.

  7. #7

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    Quote Originally Posted by David H. Bebbington
    M sync = A 20 millisecond delay in FIRING THE SHUTTER...
    The geek engineers I have breakfast with frequently would probably argue for hours about this: is M-synch really a 20ms delay in release of the shutter or a 20ms "pre-contact" of the synch before the shutter is released.

  8. #8

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    You'll pay for that "Geek" remark, Brian
    Tom Hoskinson
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    Everything is analog - even digital :D

  9. #9

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    Quote Originally Posted by BrianShaw
    The geek engineers I have breakfast with frequently would probably argue for hours about this: is M-synch really a 20ms delay in release of the shutter or a 20ms "pre-contact" of the synch before the shutter is released.
    In the case of Graflex focal plane shutters, as in the Miniature Speed Graphic whose back I removed, it is pre-contact. The flash is triggered when a strip of metal attached to the shutter curtain bridges two wires connected to the flash terminal. Since the little strip of metal is fixed to the curtain and since the curtain's speed depends on the tension setting, I don't think the "delay" is particularly constant.

    Cheers,

    Dan

  10. #10
    Ole
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    Synchro-Compur MXV shutters have it as a delay. It's connected to the self timer. But the non-MXV shutters, it's a pre-contact.
    -- Ole Tjugen, Luddite Elitist
    Norway

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