Before you can consider getting a more powerful external unit, you need to make sure
that your camera has an appropriate socket. There are two types, a small round one
(known as a PC socket) or, the more common, hotshoe socket. Both of these do the
same job of triggering your flash but the hotshoe also holds your flash in place.
The flash is synchronised with your shutter. This is why these sockets are sometimes
referred to as "sync" sockets and the cable that goes between the flash and the camera
is called a "sync" lead. Sync is just short for synchronised. On Dslr cameras, this
synchronisation will only work up to a certain shutter speed.
The power of a flashgun is given as a "guide number" (GN for short). So, if you're
choosing a flashgun for its power, this is the number you need to look for. The bigger
the GN, the more powerful the flash is and the further the distance it will cover.
Flashguns nowadays have their own automatic exposure system. This means that when
you take a picture at less than the maximum distance, the flashgun itself will reduce
its power output automatically for this reduced distance, giving you the correct
If you look at a hotshoe socket from above it will either have just one contact in
the centre or several metal contact points. If the latter is the case then you can
use a "dedicated" flashgun. These are by far the easiest type to use. This is because
they will integrate completely with your camera and work exactly the same way as
your built in flash. All the flash settings you have in your camera will work on
the external flashgun and all you have to remember to do is switch it on.
Dedicated flashguns are mostly made by the same manufacturer as the camera but some
independent flashgun makers supply units that are dedicated to specific models of
camera. These are designed to work exactly the same way.
More power is not the only advantage you get from an external flash. Because the
light source itself is now further away from the lens, the chance of getting red
eye in your shots is greatly reduced. Also, many of the external units allow you
to rotate the flash and bounce its light off the ceiling or wall.
This is extremely useful because it allows you to use flash without the associated
harsh shadows that are normally produced. You do need a nearby light coloured ceiling
or wall to do this but it really transforms the quality of the light you get from
If, for any reason, you are not using a dedicated flashgun, then things are a little
more complicated. You will need to adjust some settings in your camera to get the
best out of it. Normally, you would adjust both the aperture and the shutter speed
to set the exposure. But, when you are using flash, that rule goes out the window.
The flash fires so quickly that the shutter speed hardly matters. Except for the
limitation mentioned earlier with Dslr cameras.
To use a non-dedicated flash, you first need to find out the ISO number setting on
your camera. You then need to estimate the distance to your subject. There will be
a place on the flash itself to input your ISO number. If the flash has only one power
output available, Then just setting the ISO number will give you the range of distances
that it can cover and an aperture (f/no.). Some flashguns have a choice of power
outputs. Each one will have its own distance range and its own associated f/no. Select
an appropriate distance range and read off the f/no. You need to set this aperture
on your camera.
Go into fully manual mode and set the f/no. indicated by your flashgun. For most
situations, a shutter speed of around 1/100th of a second will be fine even for Dslrs.
The camera's exposure meter will probably tell you that you are going to get a badly
underexposed shot. Just ignore this, your camera doesn't know that you're going to
You might think that because you have to set a specific aperture that you should
use aperture priority mode, but don't. If you do that your camera will probably try
to set a very slow shutter speed to compensate for the dark conditions. This can
give you a shot with camera shake superimposed over the flash exposure.
It is worth remembering that every time you take a picture with flash, you are actually
making two exposures at the same time. One is the picture you would have taken if
the flash hadn't fired, the other is the exposure created purely by the flash. In
the most typical situation of using flash in a dark room, the light from the flash
should totally overwhelm the exposure your camera would make without it.
Both exposures are defined by the ISO and aperture, but the camera's exposure is
also affected by the shutter speed. If this is slow enough for the camera to have
exposed the picture without flash, then you will see both images in the final result.
There are times when this is exactly what you want to do. For example on a shot with
a very dark foreground but a brightly lit background. You can use the flash to balance
the foreground lighting with that of the background. Some cameras have a specific
setting for this, called "slow-sync" or something similar. This works with their
built in and dedicated guns. You can do the same thing with non-dedicated guns, but
it will take some experimentation.
A more typical example is when using "fill-in" flash. This is where the light from
the flash is used just to lighten the shadows of an otherwise normally exposed outdoor
shot. In this case the flash exposure needs to be much less than the camera's. Some
cameras may have a fixed setting for this whilst others will allow you to adjust
the flash exposure independently of the camera's. It depends on your personal taste,
but traditionally, a flash exposure setting of minus 2 seems to work quite well.
To do this with a non dedicated gun involves a bit of cheating. Once you have got
the "correct" aperture from the flash, you then set a smaller aperture than this
(higher f/no.) on the camera and use aperture priority so the camera will still give
you the correct exposure.
Many people are put off using flash because of the results they see from the camera's
built in flash. Which is a pity really, because flash is probably the most useful
and versatile light source available to the photographer. On the surface, an external
flashgun just gives you a more powerful flash, but in reality it gives you a great
deal more creative control over your photographs.
If you would like to discover what an external flashgun can do for you, why not take
a look at the extensive range available from cameras2u.com. They have many models
to suit most makes of camera, use the form on their flashguns page to find the right
one for you.
Take a look at flashguns