Pixiq

Most Canon DSLRs offer two ways to sync the firing of the flash with the shutter action: first curtain sync and second curtain sync. In order to choose between these options, it helps to review the way in which flash works with the shutter speed. When the shutter first goes off, there is a shutter curtain that drops down to expose the sensor. When the shutter speed is reached, a second curtain drops down to block light from the sensor. With first curtain sync, the flash goes off as soon as the first curtain is open. With second curtain sync, the flash does not go off right away--it “waits” until the exposure is about to end, firing just before the second curtain closes.

First curtain sync is the default that comes preset by the camera. You can choose second curtain sync in , under the item for Flash control. Flash control offers several options for the camera to deal with both the built-in and accessory flashes. Scroll to Built-in flash func. setting and press . Scroll to Shutter sync and press again. Select either 1st curtain and 2nd curtain.

There is little difference between these two choices at faster shutter speeds. As your shutter speed gets longer, however, there can be a significant difference if you have a subject that is moving through your picture area. With first curtain sync, the flash goes off right away and creates a sharp image of the subject at the beginning of the shutter speed sequence. Then the subject moves during the rest of the exposure, hopefully creating an interesting blur. But because of the timing of the firing of the flash, the result is that the movement blur appears in front of a sharp subject--not the way we perceive the blur of motion to appear.

With second curtain sync, the subject moves during the exposure first, creating some sort of blur. Then the flash goes off just before the exposure ends, creating a sharp image of the subject after the blur. The result is that the motion blur appears behind, or to be following, the sharp subject--the way we expect motion blur to appear.