Types of flash unit

Almost all cameras come with a built-in flash, and while this is undoubtedly convenient, it’s important to be aware of the limitations of such units. The main problem is the relative lack of power, although their position on the camera – very close to the optical axis of the lens – can cause problems too. These and other drawbacks lead many professional and keen amateur photographers to invest in an external flashgun. So how will you know if your built-in flashgun is good enough for what you want to do? And if you need an external unit, what sort should you get? There are four main types of flash to choose from, and each has its pros and cons.

Built-in/pop-up

The flash built into your camera has been designed to work seamlessly with the camera’s exposure metering, focusing and zoom systems, so it’s really easy to use. However, the lack of power means that your maximum shooting range may be just 2-4 metres, depending on the ISO setting you choose; this can make long-range telephoto shots impossible. Another problem is that a built-in flash exacerbates redeye effects, because it’s so close to the camera’s lens that the light shines into the subject’s eye at the same angle as that at which the reflected light is entering the camera. Built-in flash can’t be ‘bounced’ off walls or ceilings to soften the lighting effect, and it’s also possible to get problems with close-ups, because the lens can cast a shadow over the subject.

Dedicated hotshoe-mounted

An external, hotshoe-mounted flash solves many of the problems associated with a built-in flash. These days it’s easy to buy dedicated flashguns designed to link electronically with your camera’s exposure, focusing and zoom controls; as a result, they can be just as ‘automatic’ as a built-in flash. An external flash will offer a lot more power – Canon’s 580 EX has a maximum guide number of 58 (it depends on the zoom position, and hence area of coverage) – and you’ll usually get a swivelling/tilting head for directing ‘bounce flash’. The flash tube itself will be larger, producing a slightly softer light, while the greater distance between the flash and the lens will also help to reduce redeye.

Hammerhead

Hammerhead flashguns are so-called because of their characteristic shape; they consist of a tubular ‘handle’, which generally holds the batteries, on top of which is the flash head (the ‘hammer’). The flash head can tilt and swivel like those of hotshoe-mounted guns. The advantage of hammerhead units is not just their sheer power (the Sunpak Auto 622 has a guide number of 60) but the fact that they’re mounted alongside the camera on brackets. While this makes the camera/flash kit more cumbersome, it provides a better lighting angle (slightly from one side, rather than head-on), which is why hammerheads are so popular with press photographers at red carpet events.

Ringflash

Macro shots pose special problems for flash use; the camera is usually so close to the subject that it casts a shadow over it when the flash fires, and you may be unable to reduce the flash power sufficiently for subjects so close to the camera. A hotshoe-mounted flashgun will create the same problems, and while a hammerhead gun mounted to one side might not create shadows, you’ll still be left with very harsh, directional lighting. A ringflash is designed to solve all these problems; it fits on to the camera lens, so there are no shadow problems, and the round tube provides a much softer, more even illumination.