> 4 minute read

What Is Sync Speed?

The sync speed of your camera determines how fast a shutter speed can be safely used with flash. But where does it come from? And why do you need to know about it?

You might have heard the phrase ‘sync speed’ used by photographers when talking about flash photography. This is not the time it takes for your camera to reach the seabed if you drop it off the side of a boat (that would be the ‘sink speed’!), but rather the fastest shutter speed at which your camera can synchronise with flash to produce a properly exposed flash photo.

For most cameras in the X Series, this critical shutter speed is either 1/180 or 1/250 sec. Go any faster than this and you risk seeing black bars across the frame where the very brief burst of flash has not illuminated the scene properly.

If you make images in automatic modes, like SR AUTO, then the camera will take care of selecting the correct shutter speed, so you’ll never have to worry about this. But if your aim is to get away from auto modes in the future and take some creative control over your photography, then it doesn’t hurt to understand where the sync speed limitation comes from and how to get around it.

The Origins of Sync Speed

To understand where sync speed comes from, we need to understand how the shutters in X Series cameras operate. The shutter consists of two metal curtains: the first moves out of the way and exposes the sensor to light; while the second follows it to cover the sensor and end the exposure. This type of shutter is called a focal plane shutter and is used in all X Series cameras (apart from X100 models, which use something called a leaf shutter).

As we select faster shutter speeds, the time between the first curtain opening and the second one closing gets less and less, until we reach a point where the second curtain needs to start closing before the first one has opened fully. In this way, the curtains can be thought of as forming a slit that moves across the sensor, exposing it a little at a time.

This fastest shutter speed where the curtains open fully, and don’t form a moving slit, is the camera’s sync speed.

1/250 SEC

1/320 SEC

1/400 SEC

1/500 SEC

If we activate a flash during an exposure where the shutter is fully open, the light from the flash illuminates the whole sensor and gives us a complete picture – no problems there. But if we activate a short burst of flash when only part of the sensor is revealed, then only this part of the sensor is illuminated – the rest will be dark and will give rise to the ominous black band we see when using flash at shutter speeds faster than the sync speed.

As flash technology has become more advanced, new ways to overcome the sync speed threshold have become available, which let photographers use flash at much higher shutter speeds than the sync speed, and we’ll look a little at these later on in this series of tutorials.

In the meantime, you can avoid the strange black lines in your pictures by making sure the shutter speed is at or below the sync speed limit when you’re creating with flash. This is likely to occur when using flash in bright conditions, rather than in dim light, since this is when you’ll be looking to use these short shutter durations anyway.

Your Next Steps

• CHALLENGE Try making some flash pictures for yourself using shutter speeds below and above the sync speed. Can you see the dark band caused by the second shutter curtain? Post your images to social media with the hashtag #learnwithfujifilm and #flash. You can also submit your work here for a chance to be featured on our social media channels