Setting up your camera for studio flash
The principles explained here apply to all studio flash units and all digital cameras, but of course the details will vary depending on your camera, so you’ll need to read your camera manual in conjunction with this guide.
The first thing you need to understand is that the metering system in your camera is designed to work only with continuous lighting, such as daylight, so the exposure and camera settings that work with continuous lighting are different when using flash. This is very straightforward, once you understand the principles.
Here are the things that are relevant to studio flash that are different to shooting with continuous light:
1. Shutter speed
2. Lens aperture
3. Measuring the light
4. White balance
5. Firing the flash
Shutter speed:
With continuous light, the shutter speed matters because the choice of shutter speed controls or prevents subject blur and also works in conjunction with the lens aperture to control the exposure.
For example, you might want to choose a fast shutter speed, say 1/2000th second, to get a sharp picture of your child playing on a swing. If you set your camera’s shutter speed to (say 1/2000th in S or TV mode then the camera will measure the light and set a wide aperture that will ensure a correct exposure.
But, with studio flash, the only real function of the shutter is to be fully open when the flash is fired. Unless there are abnormally high levels of continuous light present (such as sunlight streaming through a window) the shutter speed won’t affect the exposure, so you need to set your camera to MANUAL and you set the shutter speed to a speed at which the shutter will be fully open.
Let me explain that. On point & shoot digital cameras, there is no shutter as such, just an electronic function that does the same job. On most point and shoot cameras, you can use any shutter speed available on the camera – but DSLR cameras work differently 
and have a focal plane shutter (a shutter immediately in front of the sensor) that is, in effect, just two blinds. The first one opens, uncovering the sensor, and the second one then closes, so at slow shutter speeds the sensor is exposed to the light for a moment. When using flash, the flash has to fire at that moment.
So far so good, but at faster shutter speeds the second curtain starts to close before the first one has reached the end of its travel, so what you get in effect is a moving slit that travels across the sensor and exposes a bit of it at a time. That’s no good for flash, because flash needs the shutter to be fully open at the time of the flash. If it isn’t fully open then part of the image will be covered by the shutter and you’ll get a black line covering part of it.
The picture above left is in fact the shutter of a film camera, because the insides of film cameras are accessible, but the shutters in DSLR cameras are the same.
So, you need a slow shutter speed – one at which the shutter is fully open at the time of the flash. This varies from camera to camera. Most camera manuals state that their model will work at around 1/250th second but in reality that can be optimistic, because the manufacturers are assuming that you’re using a dedicated hotshoe flash, not a studio flash, which may not work properly at that speed.
So, to make sure that your studio flash will work properly with your camera, set a lower speed. 1/125th second is normally safe with a camera that claims to work at 1/250th.
I said earlier that using a slower shutter speed won’t affect the exposure in any way. That’s true because, in most indoor shooting situations, the amount of light is insignificant compared to the power of your flash. Don’t take my word for it though, test it for yourself!
1. Set your camera up to work with your flash, at whatever aperture gives the correct exposure, and with the camera set at say 1/125th.
2. Switch off the flash, so the only light available is the continuous light in the room
3. Take a shot. If the viewing screen is black then you can see that there isn’t enough light in the room to affect the shot.
4. Repeat this test at different speeds, say 1/60th and 1/30th. If the screen is blank you’ll know that the shutter speed isn’t too slow and that the shutter isn’t letting in enough light to affect the shot.
Also, it’s worth remembering that the shutter speed has virtually no effect on subject blur either, in a studio shooting situation. The flash of light is extremely brief and it’s the flash that freezes the movement, not the shutter.
The shutter speed set on the camera does have SOME effect on freezing movement when using flash indoors, but its effect is far more limited than most people think. What really makes a difference is the flash duration. In effect, the flash becomes the shutter.
Flash duration is expressed as t.5. What t.5 is, in practical terms, is the length of time it takes for half of the flash power to be discharged. Now, the Lencarta ElitePro 300 flash head has a very short t.5 time of 1/2000th second, which means that half of the flash power has been discharged in just 1/2000th of a second. The other 50% of the power tails off relatively slowly, and so doesn’t have much effect, but a fast shutter speed will ‘clip’ more of the 50% remaining power than a slower shutter speed, and that’s why it can make SOME difference if a faster shutter speed is used.
Take a look at these photos, all of which are straight off the camera, with no post processing applied.
As you can see, the subject here is an electric fan, the fan blades are moving far too fast for any studio flash to ‘freeze’ the action, so each of the shots has quite a lot of movement blur. There is SOME difference in the amount of blur between the different shots, but even with this very fast moving subject, the difference is fairly small. The flash has done a pretty good job of freezing the movement.
A cheaper flash head will typically have a much longer flash duration and so can’t freeze movement nearly as well. If you need to freeze movement to the maximum you’ll need to use a hotshoe flashgun, which works in a different way, and which can produce extremely short exposures when used at low power. Even a hotshoe flash can’t freeze all movement and very specialised, special purpose flashes are needed for some subjects.
So, is it worth using a high shutter speed with flash?
It may make a difference, but the difference may be too subtle to see, unless you’re photographing something as fast as moving fan blades.
So, if you do want to use a high shutter speed, how high can it be?That depends on the type of shutter in your camera, as we've already discussed, and the means of firing the flash.
The method used to fire the flash is important too. When camera manufacturers say, for example, that their camera will work with flash at 1/250th second they are assuming that you are using a hotshoe flash manufactured by them, and that it is either plugged into the camera hotshoe or connected to the camera by means of a hard wire. In either case, the electrical connection has no effective delay because the electrical signal that links the shutter and the flash together travels at the speed of light. The same applies if you connect the flash to your camera with a synch cord, which plugs into both the light and the camera – but this method is unpopular because it’s clumsy, subject to unreliability because of poor electrical contact and because many modern cameras don’t have a PC (synch) socket to plug the lead into, so most people use a radio trigger instead.
Unfortunately, even the very best radio triggers have SOME delay in the system, even if that delay is only 1/2000th sec or so. What this means is that the second shutter curtain may have started to close before the flash has fired, and you may end up with this unexposed section on your image if you use the fastest speed at which flash can theoretically be used.
In fact, some of the cheap and cheerful radio triggers have such a long delay that they will only work at 1/30th second!
Some cameras can’t be used at the fastest theoretical synch speed for some models of flash head but can be used with other models of flash head. Flash heads that can’t synch well at maximum synch speeds with some cameras work perfectly well with other models of camera, so the problem seems to be related to communication between certain cameras and certain flash heads, rather than to ‘faults’ with either the camera or the flash head. Whatever the reason, the problem is usually solved by setting a slightly slower shutter speed.
What have we got so far?
1. It’s the flash, not the shutter speed that freezes action
2. The only function of the shutter is to be fully open when the flash fires
3. Under normal indoor lighting conditions, there’s no point in using a high shutter speed
4. Your studio flash may not work properly if you use the fastest theoretical synch speed for your camera
5. The triggering delay on your radio trigger may prevent the fastest theoretical synch speed for your camera from being used
Let's move on to the other things that matter:
Lens aperture
This is the main control of your exposure. You set the aperture that produces the correct exposure. If you want to use a smaller aperture you’ll have to turn up the power on your flash heads, if you want to use a larger aperture you just turn the power down, or reduce the power in some other way, for example by putting neutral density gels over your lights or a neutral density filter over your camera lens. You can also change the ISO setting on your camera. Moving the lights further from your subject will reduce the effective power too, but that’s a bad choice because changing the distance will affect the quality and the effect of the light.
Measuring the light
If you use your camera with continuous lighting in any camera setting except manual the camera will measure the light reflected from the subject and will automatically set both the shutter speed and lens aperture (programme mode), the shutter speed that suits the aperture (A or AV mode) or the aperture that suits the shutter speed (T or TV mode on Nikon or Canon cameras).
But that doesn’t work with studio flash because your camera meter can’t measure the very brief flash. 
You need to measure it with a flash meter, or you can manage without a meter and either guess the exposure, checking the viewing screen to see whether it looks OK or checking the histogram, which is helpful as long as you aren’t shooting with a ‘blitzed’ white background (turn off the lights on the background if you are).
White Balance
Setting the white balance on your camera will tell it the colour temperature of your light source and will set the balance needed to obtain neutral colours. If you’re using continuous lighting you can set auto white balance, which sometimes does a good job of getting the white balance right – but of course this doesn’t work with studio flash because the camera can’t measure the colour of the brief flash of light – and anyway, it doesn’t know whether you want it to measure whatever other light is there or to measure the flash, so you need to set the white balance manually.
Any digital camera will normally allow you to set a ‘custom white balance’. How you do this will be explained in your camera manual.
Another method is to set the colour temperature of your lights on your camera, either by telling the camera to set the white balance to a symbol or by setting an actual colour temperature on your camera. 
If your camera allows you to set the actual white balance then you would normally set it to 5500K because that’s the theoretical colour temperature of studio flash (although many of the cheaper flash heads produce very variable colour temperature, especially at the lower power settings).
If your camera has symbols instead of an actual colour temperature then you’ll just have to find one that produces acceptable results. ‘Flash’ is the obvious one to try but it’s intended for use with hotshoe flashes and is isn't always right when using studio flash. ‘Hazy sunlight’ and 'flash' are usually in the right ball park and are worth trying.
All of these settings apply when you’re shooting JPEGS. If you’re shooting in raw then whatever colour temperature you set on your camera will act as nothing more than a marker, you set the required colour temperature when you process the image from raw. The best way of doing this is to include a colour target in a setup shot – a grey card or, preferably, a Macbeth TM colour checker, then use the eyedrop tool to sample grey on your colour target and adjust the image colour on all shots taken under the same lighting conditions.
Of course, the term ‘correct’ really means ‘neutral’. A lot of photographers prefer the tones to be slightly warmer than ‘correct’ and so set the colour temperature to suit that preference.
The shot on the far left is 'correct' in that the colour balance matches the actual colour of the background. Each shot to the right is then 200K 'warmer' than the last.
Firing the flash
This is the means by which the camera tells the flash to fire at the right time, in other words the means by which it tells the flash to fire when the shutter is open. There are various ways of doing this.
As mentioned earlier, the traditional method is to plug a synch cable into both the camera and one of the flash heads. Your camera will need a PC synch socket, which many don’t have, although you can get a simple adapter that fits into the camera hotshoe and which terminates in a synch socket. Some makes and models of camera are easily damaged by the voltage carried in the synch cable, so don’t use this method unless you know how much voltage your camera can safely handle AND you know the trigger voltage used by your studio light. In fact, it’s probably better not to use that method anyway, because it’s inconvenient and unreliable.
A hotshoe flashgun fitted to your camera can trigger the lights if you wish, provided that you have one that doesn’t fire a pre-flash that can’t be turned off. A pre-flash is a low-energy flash used to measure distance or to reduce redeye, and if it can’t be turned off then it will fire the studio flash before the camera shutter opens!
If you use a hotshoe flash to trigger your studio flash you’ll need to turn the hotshoe flash right down, so that the flash doesn’t affect your lighting too much.
Infra red transmitters are more convenient than synch cables and were the next step beyond flash synch cords. They simply plug into the hotshoe of your camera and emit a low powered infra red flash when the shutter is fired, which is picked up by the slave sensor on your studio flash. This method can work well provided that the slave sensor is sensitive to infra red light, as long as you’re not too far from the studio flash, as long as the ambient light levels aren’t too high, and as long as you have approximate line of sight between the transmitter on the camera and the sensor on the flash – they don’t work if the flash is behind the photographer and may not work if the flash is behind the subject, depending on the design of the flash head and on whether or not it’s fitted with a modifier such as a softbox, which can block the light from the transmitter.
Radio triggers are the preferred method.
Radio triggers consist of a small transmitter which is plugged into the camera hotshoe and a receiver which is plugged into the studio flash.
The transmitter sends a signal to the receiver that will work either with or without line of sight and which will also work if there happens to be a brick wall in the way!
Radio triggers are available in a vast range of different prices and with different specifications and different levels of reliability and build quality.
It’s a good idea, for most people, to get one that offers a choice of channels – then, if you’re getting interference on one channel you can simply switch channels, just the same way as on a two way radio. As mentioned earlier, there is a slight delay when using radio triggers, and this can sometimes restrict the shutter speed that can be used.
Whichever triggering method you use, you’ll only normally need to fire one flash head. Any other flash heads will fire automatically when they 'see' the flash from the one fired by the camera. I say ‘normally’ because there may be situations in which you want to turn off the slave sensors on the flash heads so that they don’t fire at the same time – for example if you’re a wedding or an event photographer you’ll need to turn off your flash sensors to stop your flashes being fired by other photographers who are using flash, and the same goes if you’re shooting in a studio in which other photographers are also using flash. In these situations you’ll need to connect a radio receiver to each flash head.