Sync terminology questions

Discussion in 'Lighting' started by narsuitus, Dec 15, 2005.

  1. narsuitus

    narsuitus Member

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    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. rbarker

    rbarker Member

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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. :wink:

    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"? :wink:

    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.
     
  3. Charles Webb

    Charles Webb Member

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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. Helen B

    Helen B Member

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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. David H. Bebbington

    David H. Bebbington Inactive

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    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. Donald Qualls

    Donald Qualls Member

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    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).
     
  7. BrianShaw

    BrianShaw Member

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    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. Tom Hoskinson

    Tom Hoskinson Member

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    You'll pay for that "Geek" remark, Brian
     
  9. Dan Fromm

    Dan Fromm Member

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    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. Ole

    Ole Moderator Staff Member

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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.
     
  11. BrianShaw

    BrianShaw Member

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    I was refering to those other guys... you might be an engineer but you're not a geek, Tom. See you Monday? :smile: