What is x-sync?

Discussion in 'Medium Format' started by eddy_yu, Oct 1, 2004.

  1. Hi all,

    I saw it somewhere that people say max x-sync speed at 1/250 is not
    enough for studio shutting, but what exactly is x-sync? I guess it's
    to make the shutter and flash both fire at 1/250 speed? if so, I
    guess it's enough for studio use.

    hassy H1 has it up to 1/800 i believe and is it really all that
    useful? Sorry i am still new to studio kinda thing. thanks.
  2. "...but what exactly is x-sync?"<p>The fastest shutter speed at which the shutter (focal plane type) is fully open. Google "focal plane" shutters.
  3. "X-sync" is the flash synchronization setting to be used with electronic flash units (nowadays that means all flash units).<br><br>There are/were different synchronization settings because different types of flash (bulbs) took different amounts of time between start of ignition and the moment they burned (literaly) brightest.<br><br>Electronic flash units reach full power output instantly (as good as).<br><br>It is important that the moment of maximum burn coincides with the moment the shutter is completely open.<br>Using leaf shutters (a.k.a. central shutters) this is not a problem; they open completely at all speeds.<br>Focal plane shutters however work by removing one curtain from the film gate, replacing it with another one after a selectable but preset amount of time. With short shutterspeeds the second curtain is already covering up some parts of the film while the first curtain is still moving to expose other parts: the film is not completely uncovered then. So if a flash is fired at these speeds, only part of the film is exposed.<br><br>The maximum x-sync speed is the fastest shutterspeed at which the film is completely exposed.<br><br>It is important to have a high maximum sync speed if you want to use fill-in flash in bright light (for instance to fill in shadows in bright sun lit scenes), and still keep some control over what aperture you can use.<br>Bright scenes of course require small apertures and/or fast shutterspeeds. If the max. sync speed of a camera is slow and you do want to use fill flash in bright light, you will have to close the aperture until the correct setting is reached for the parts not needing fill flash. This typically means very small apertures, and the effect on depth of field that comes with that. Not always wanted. And because aperture alone control the effect of flash, you may need a very powerfull flash unit to be able to get the desired fill effect.<br><br>Whether you need a high sync speed or not depends on what you do. In the studio, you do not really need high sync speeds, no.
  4. In the simplest of terms, it's the speed or speeds at which a strobe will sync with a given type shutter. You wrote: >>> I saw it somewhere that people say max x-sync speed at 1/250 is not enough for studio shutting,...."<<< Exactly what is "not enough for studio shutting (shooting?)?" Where did you read or hear this, and what do YOU think it means? I think you should read some books on basic camera functions.
  5. Older cameras (made at the time electronic flash, flash bulbs, and flash cubes were available usually had a switch on the shutter to select the type of flash you were using. see Kodak Retinas and Agfa Solinettes as examples.
  6. X stands for

    the gas type in the strobe lamp. X synch is fired when the shutter is wide open. Many leaf shutters synch at the full top shutter speed. This allows more control in fill flash applications. X synch is old; going back to WW2 and some before. The Kodka Medalist II has X synch.
  7. In the old days, there were three types of flash synchronization: x (instantaneous), f (5 milliseconds) and m (20 milliseconds). F and M sync were used for flash bulbs. The bulb was fired before the shutter was fully open to allow for the delay reaching full intensity: 5 ms for gas bulbs (clear with a single, short filament) and 20 ms for wire-filled bulbs. At X-sync, the flash is fired at the instant the shutter is fully opened.

    The maximum synchronization speed is that speed where the shutter is fully open. Leaf shutters are always fully open at any speed, but focal-plane shutters are partially closed above the maximum X-sync speed, with a slit that drags across the film opening.

    That didn't matter with flash bulbs, since the duration was so long that you could use nearly any speed. (There were special, long-duration bulbs for focal-plane shutters). Electronic flash duration is generally much shorter than the traverse time (x-sync speed) of a focal-plane shutter. That's not necessarily true with studio flashes. In order to put out more light using high-impedance (e.g., electrolytic) capacitors, the duration can be as long as 1/100 of a second. Using a higher shutter speed, even a legal x-sync speed, would reduce the light reaching the film.

    Slower sync speeds make ambient light a concern. Since one normally controls the ambient light in a studio to an appropriate level, the question is moot. It does matter when using fill-flash outdoors or in bright artificial light.
  8. It's the fastest speed a boat can troll without outrunning the fish.
  9. "Leaf shutters are always fully open at any speed" - this is correct for all practical means. In reality, any stage of openning central leaf shutter exposes light over entire film frame. If central shutter just stars openning a bit (like a pin hole), the light covers entire film frame. X sync, even if not precise will always expose entire frame (more or less light - depends on the electronic unit speed and the shutter speed, and the X sync usually set when leaf is wide open) Electronic flash durations vary from 1/200 sec to 1/10000 sec, depending on model and needed power output. Therefore X- sync for leaf shutters has a bit different meaning than for focal plane shutters, as the light will always expose entire film to some degree. E.g. flash with 2500 WattSecond may take 1/200 sec to fully discharge, and the rated guide number will not be achieved if leaf shutter speed was set for 1/500 sec.

    Focal plane shutter speed is regulated by the size of the narrow slot (or slit) between front and end curtains, and also by the speed of the shutter moving across the frame. Shutter speed setting when shutter slot is as wide as the width of the frame is called X sync. For vertically traveled shutters, shutter speed setting when shutter slot is as wide as the height of the fils frame is calles X sync.

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