Typically, our route into photography will involve buying a DSLR, then some more lenses, and then maybe a nice camera bag. At first, our photographic expectations will be well met by our camera’s capabilities in almost every area, except one: flash. As novices, we may use the popup flash that our camera provides, and accept the results. However, like buying new lenses, adding a dedicated external flashgun can add a huge amount of creativity to our photography.
Buying a flashgun
When you first research the purchase of a flashgun, you may be daunted not only by specifications but also the odd numbers you see in the specifications. Don’t be put off by this. These numbers are not vital, though having an understanding of them will help you not only in your purchase, but in the way you use the flash.
Flashguns should be a carefully considered part of your kit
Image by Keith Williamson via Flickr
The number you will see most often is called the guide number. Simply put, this is a number that tells you how powerful the flashgun is. Typically, you will see this number expressed as: 80 feet at ISO 100. What this means is that, with your lens set to f/1, and your ISO set to 100, the flashgun will illuminate a subject 80 feet from you.
Of course, nobody has f/1 lenses, but for every one stop down, the amount of light reaching the subject is halved. So, if you are using a lens set to f/2.0, the usable range of the flash will be 20 feet. When considering your purchase, consider this number carefully.
The next decision you need to make is whether to buy a flash from your camera’s manufacturer or from a third-party company. In your camera’s manual, it will almost certainly recommend that you use a flash from the same manufacturer. This, however, is a marketing ploy. Third-party flashguns will work perfectly well with your camera, will often be cheaper, and might have more functions.
Should you decide to go with a third-party manufacturer, there is one important consideration, and that is flash dedication. Flashguns have become so sophisticated that they are designed to work only with a particular manufacturer’s cameras. The electronics in the flashgun have to be able to decipher the information coming from that camera. This is called dedication. When choosing your third party flash, you simply need to remember to buy one that is dedicated to your camera manufacturer. So if, for example, you choose to buy a flashgun from Metz for your Canon EOS 7D, make sure the flash is dedicated to Canon.
Lastly, when buying your flash, look for one that has at least a bounce facility and, better still, a swivel capability. Bouncing means that you can point the head of the flashgun upwards toward the ceiling and away from the subject. The big advantage to this is it produces a much softer, diffused light compared to the harshness of a direct flash. Swivel is basically the same, but allows for the flash head to be rotated in the horizontal plane as well, meaning you can bounce the flash off walls or similar surfaces.
The soft, diffused light from bounced flash
Image by Iain Cuthbertson via Flickr
Using your flash
Once your new flashgun has arrived, how do you use it? As I mentioned, most flashes are dedicated. Your camera will have a flash mode called Auto TTL or something similar. When you take a picture with the flash attached, the camera will send shutter, ISO, and aperture information to the flashgun. When the shutter is pressed, the flash will know exactly how much power to use on the subject. This will work even when the flash is being bounced from a ceiling.
However, it is not infallible, and for this reason your camera will have a flash exposure compensation mode. This works in much the same way as your camera’s exposure compensation, allowing you to increase or reduce the exposure by adjusting the power of the flash output. For example, if you find that your images are constantly being overexposed, you can reduce the flash output by half or one full stop to compensate.
As well as the TTL mode, your flash will have a manual mode. When you set this, you are directly setting the power of the flashgun with no external information from the camera. The settings are expressed as fractions of full power, so setting half will give you half the flash output of full power and so on.
The biggest advantage to using a manual flash setting is in situations where the distance between your flash gun and your subject is always the same. For example, consider a situation where you are shooting different people as they enter a function room at a distance of 10 feet and using manual flash. So long as that distance to subject was the same for everyone entering the room, each image should be identically exposed. Auto flash modes can actually be at a disadvantage in this situation. For example, if you get two people wearing black, then someone wearing a single bright color, your camera will meter these frames differently, sending changing settings to the flash. Instead, with a single manual setting, the result is a consistent flash output for every shot, and each image should be identically lit.
Most modern flashguns will also have other modes. Some of these are set from the camera’s menu system; some on the flash itself. These modes can include red eye reduction, rear curtain sync (a mode that allows you to add some motion blur to moving subjects), and slow sync.
Image by Richard Melanson via Flickr
The effect of rear curtain sync
The last important information to note is the flash synchronisation speed. This is a specification of your camera, not the flash, but is important to understand. There is a maximum shutter speed at which flashguns can be operated. Typically, this is around 1/250th of a second, but some cameras with certain flashguns can go much higher. By default, cameras will usually not fire the flash if the shutter speed is too high.
The relevance of sync speed is most important when shooting flash outdoors, otherwise known as fill-in flash [editor’s note: this is commonly called fill flash in the US]. If, for example, you are shooting portraits on a brightly lit beach, but want to use fill-in flash to illuminate the model’s face, you might find that you cannot get the shutter speed below 1/250th of a second to sync with the flash. It is also important to know that, apart from maximum sync speed, flashguns are not affected by the shutter speed on your camera. They are affected only by aperture and ISO.
Image by Kevin Cole via Flickr
Buying a flashgun is often an afterthought to new photographers, but getting one is a great way to improve your creativity. Modern flashes take away the hard work of calculating the right power settings, leaving you more time to think about the composition of the shot.