What is flash sync? Your flash modes and when to use them (free cheat sheet)

How your flash modes work: free photography cheat sheet from Digital Camera World

What is flash sync? If you’re new to flash photography you’ve probably been asking yourself this question. In our latest beginner’s guide to flash photography we explain how each of your flash modes work and offer a handy photography cheat sheet that illustrates the process.

Flash modes explained

For many people, flash is that horrid burst of light that ruins indoor photographs, stripping scenes of all atmosphere whenever it goes off. However, when it’s used correctly, flash can be the saviour of many an image, and shouldn’t be confined to being used in darkness.

For example, a subtle burst of flash can be used to fill in shadows when shooting portraits of people with their backs to the sun. This means no more squinting, or dark shadows where the eyes should be. Instead, the flash turns what might otherwise be a silhouette into an evenly lit image. Here’s a quick guide to what you need to know about your flash modes…

What is flash sync?

Traditionally, the flash operates at 1/60sec. This means that when you’re using flash, the shutter speed is set to 1/60 sec and the flash is synchronised to fire while the shutter is open.

However, modern cameras take advantage of the fact that the flash duration is extremely short, and offer higher ‘sync’ speeds of around 1/200 sec or 1/250 sec.

Naturally, there’s nothing to stop you using slower shutter speeds, and this can be particularly useful for balancing the illumination of the flash with ambient lighting for a more natural look. This is often referred to as ‘slow-sync’ flash.

Sync speeds

Interestingly, the shutter speed is often not a significant factor in the flash exposure calculation. The way that the ‘focal plane’ shutter of your camera works means that you do not have the full range of your camera’s shutter speeds on offer anyway.

In normal flash modes, you need to ensure that the shutter speed is set at or below the ‘sync speed’ for your camera. DSLRs have sync speeds of either 1/200 sec or 1/250 sec, depending on the model; if faster shutter speeds are used then part of the image will be obscured by the falling shutter curtain.

Fortunately, most of the factors that need to be taken into consideration when calculating flash exposure are handled by the camera. A suitable sync-friendly shutter speed is set for you, unless you use the camera’s Manual (M) exposure mode – and as long as you are using the pop-up flash or a dedicated hotshoe flash.

An extra complication is that flash has a relatively limited range. The maximum power varies between the flash used – but once the subject is more than a few paces away, flash has little effect. This ensures that there are plenty of subjects where the use of flash is impractical.

What is flash sync? Digital Camera World explains

PAGE 1: What is flash sync?
PAGE 2: Rear curtain sync, red-eye reduction and flash metering
PAGE 3: How your flash modes work (free cheat sheet)
PAGE 4: Built-in flash vs off-camera flash


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