Advanced flash control
Once you’ve mastered off-camera flash, there are still a few advanced techniques you’ll want to master
You’ve got to the point where you’re triggering Speedlights off-camera, and getting great results. However, there’s more to flash photography than getting the right power and light placement.
This is where advanced flash techniques come in. Whether it’s utilizing high speed sync to enable the use of flash at high shutter speeds, determining whether the flash fires at the beginning or the end of the exposure, or pulsing the flash throughout a long exposure to record several images in a single frame, these advanced modes enable you to get really creative with your flash photography. Let’s see what’s on offer…
high-speed sync
Usually, you can only use flash at relatively low shutter speeds, known as the flash sync speed, which is usually 1/200 sec or 1/250 sec, depending on your camera model. This is because the shutter mechanism actually consists of two ‘blinds’, one of which is fully open and the other fully closed at the beginning of the exposure. At higher shutter speeds, one shutter blind begins to close before the other is fully open, so the image is actually exposed through a moving slit, and the blinds would show as dark bands in your image. High-speed synchronization (HSS) overcomes this by
firing a rapid pulse of flashes for the duration of the exposure, but as a result the maximum flash power is greatly reduced. It’s great for ‘fill-in flash’, where you want to brighten the facial features in a portrait taken at a wide aperture on a sunny day that would otherwise be plunged into shadow, or lighting your subject in action shots that demand a high shutter speed.
front-curtain flash
With the default front-curtain flash option turned on your flash will fire at the beginning of the exposure, and the remaining time your shutter is open will be lit by only ambient light. You won’t be able to see this at an exposure length of, say, 1/250 sec, but slow that shutter speed down to 2 secs or so and you’ll clearly see the flash goes off at the start.
rear-curtain flash
The opposite to front-curtain, rear-curtain flash will trigger at the end of your exposure. This is useful if you want to capture motion of a subject before freezing them with a pop of flash, for example a speeding cyclist or a fast car; with frontcurtain flash they’d look as if they were moving backwards!
stroboscopic mode
This as a creative way of capturing a sense of movement in a single frame and is usually combined with a long shutter speed. You set the number of flashes and frequency, measured in hertz. You’ll need a dark environment, and the pulsing of the flash during the exposure freezes the subject in different positions as it moves through the scene, as you can see with the dancer to the right.