How advantageous is a flash x-sync of 1/500s?

[ebann]

In other words, what can be done with it which will produce shots that will impress others who don't have it?

[JohnMarshall]

Hi,
It will reduce the effect of any ambient light, possible to the point that the ambient light is not recorded at all and the only light that is recorded is from the flash.
John

[Curtis N]

Compared to an X-sync speed of 1/250, the advantage is one stop, or 1.4x the effective distance, when competing with ambient light.

Suppose your flash has a guide number of 100 feet.
In bright sunlight, 1/250 and f/10 will properly expose the ambient.
Guide number divided by aperture equals distance, so
your effective range for full flash illumination is 10 feet (100/10=10).

But if you could sync at 1/500 then you could open up the aperture one stop
and use 1/500 f/7.1 for the same ambient exposure.
Now your effective range is 14 feet (100/7.1=14).

The other possible advantage is the narrower depth of field you get with the larger aperture. This can be accomplished through other means, like using a neutral density filter or high speed sync. But a ND filter won't increase your effective distance, and high speed sync will shorten it.

[Wilt]

In other words, what can be done with it which will produce shots that will impress others who don't have it?


You can go outside in bright sunlight and shoot with ISO 100, at 1/500 f/6.3 (equivalent to Sunny 16 rule, 1/ISO f/16) and be able to use a flash unit to provide the fill out to greater distance. For example, 580EX would allow you to provide fill out to 25' at f/6.3 with coverage for a normal lens, but only out to 17' if you were limited to 1/250 as your flash synch speed (HSS loses power the faster the shutter speed, so this is not a solution to limited distance fill)

[ebann]

What exactly does it mean to x-sync at 1/500s? The pre-determined flash output is all done in 1/500s? I assume that one would be in Tv mode and set the shutter speed to the x-sync speed right? I get a little confused with the concept of two-images-in-one-shot when using flash... I thought we are aiming to get the flashed subject *and* background. Having a faster shutter will yield less of the background. Is that a desirable thing? Is part of getting a better bokeh?

[Wilt]

What exactly does it mean to x-sync at 1/500s? The pre-determined flash output is all done in 1/500s? I assume that one would be in Tv mode and set the shutter speed to the x-sync speed right? I get a little confused with the concept of two-images-in-one-shot when using flash... I thought we are aiming to get the flashed subject *and* background. Having a faster shutter will yield less of the background. Is that a desirable thing? Is part of getting a better bokeh?

Your shutter is fully open for this amount of time (i.e. the entire sensor is uncovered all at at the same time...

-----------OOOOOOOOOOOOOOOO--------

...and the flash outputs light for this amount of time...

-----------!!!!!!!!!!!!!!!!!!!!!!!!!!!!!-----------

...so your shutter is fully open for the entire duration that the flash is outputting light. The entire sensor is exposed to the flash.


But if you exceeded the X synch speed (too high of a speed),
your shutter is partially open for the entire duration that the flash is outputting light.

-----------oooooooooooooooooooo---------

the flash outputs light for this amount of time

-----------!!!!!!!!!!!!!!!!!!!!!!!!!!---------------


So as a result, the last part of the shutter-open time gets no light from the flash to the sensor, resulting in a dark band in the photo along one edge

[Curtis N]

A limited X-sync speed is a reality of the focal plane shutters used in SLR and DSLR cameras. With most of today's DSLRs, at speeds faster than 1/250 the second shutter curtain starts to close before the first curtain is completely open. Since there's no moment when the shutter is completely open, it's not possible to expose the entire frame with flash at shutter speeds faster than 1/250.

Cameras with faster X-sync speeds use CCD sensors and electronic shutters. The effective shutter speed is determined by the sensor being turned on and off. This side-steps the problem of focal plane shutter curtains and allows flash to expose the entire frame, even at relatively fast shutter speeds.

I wouldn't use the term "better bokeh" because that's a subjective measurement and characteristic of the lens used. But being able to use a faster shutter speed does allow for a wider aperture in bright conditions, and a wider aperture will yield a blurrier, less distracting background.

[airfrogusmc]

It can really help when with fill flash bringing the available down on a bright sunny day, want to shoot at a large aperture or if you don't have a powerful strobe .