Slow sync flash is a technique that's used in unison with a long shutter speed. It's used to capture any movement within your shot along with a still image too. This happens because the movement is captured throughout the long exposure with the ambient light but then a still of the movement is captured too as the light from the flash bursts onto it. There are two flash options on your camera which will accomplish this technique but in opposite ways, they are know as 'Slow-Sync' flash and 'Rear-Sync' flash and I am going to be explaining these in more detail throughout today's post.
As you can see in the diagramn below, rear-sync captures the movement trailing behind the subject, as you would expect to see it, however, if the flash fires at the beginning it will make the subject look as though it's moving backwards creating a rather odd looking picture.
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Slow-Sync Flash:
As the diagramn shows above, this option will fire the flash at the beginning of the exposure, freezing the movement first and then capturing the trail of movement. It's generally best to avoid this technique though as it will make your subject matter look as though it's moving backwards rather than forwards. This is shown in the image below, as you can see, the woman has just hit the snooker balls but it looks as though they are moving back into the centre not away from it.
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Rear-Sync Flash:
This is the best flash type to use for capturing movement as it will fire the flash at the end of the exposure opposed to at the beginning, creating a more accurate representation of the trail of movement. As you can see in the shot below, this is how the image should look to accurately display the movement of the snooker balls.
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I hope this post has helped you to understand these flash techniques a bit more, if you'd like any more help then check out this website here where I got all my examples from as I found it explains it very simply and clearly.
Thanks for reading!












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