Photographic Studio Lighting by Garry Edwards
Using the modelling lights
The modelling lamp is a simple continuous (tungsten) light that's placed very near to the flash tube. Its function is to show the effect that the flash will have. At least, that's the theory but unfortunately modelling lights don't always do their job very well, and can provide misleading information. My reason for saying this is that although you may have a number of flash heads of varying power, they may all be fitted with the same or a similar modelling lamp. For example, I have lights from one manufacturer of 1200 watts, 2400 watts and 4800 watts - and they are all fitted with the same power modelling lights, 300 watt halogen lamps. And I have lights of another make ranging from 200 to 800 watts, and again they all take the same lamp, in this case 150 watt 'ordinary' ES lamps.
Now this can be very confusing because the modelling light actually falling on the subject bears absolutely no relation to the power of the flash itself and can give the impression that fill and effect lights are just as bright as the key light! And although the modelling lights can be set to give off either their full light or proportional output, which reduces as the power of the flash is reduced, this makes absolutely no differences to the error factor. So what's the answer? Well, my answer is to use the modelling light only on the key light. This shows me exactly what the key light is providing in terms of lighting effect, and helps with focussing. I see no point in using the modelling lamps of fill and effect lights on a continuous basis, and just switch them on for long enough to make sure that they are covering the required area - and, equally importantly, that they aren't spilling on to somewhere they shouldn't.
If honeycombs (grids in America), snoots or spotlights are used it's essential to check the lighting effect with the modelling lamp, but it can be equally essential to switch them off as soon as possible because these accessories restrict ventilation and too much build-up of heat can lead to an attention-grabbing and very expensive bang! And, if like me you use Elinchrom lighting you'll probably be surprised to find how short a life the modelling lamps have and how much they cost! One final point about modelling lamps - they are placed fairly close to the flash tube and the difference in position doesn't usually provide misleading information, but this difference is enough to cause problems with accessories such as focussing spotlights, especially when gobos are used to project a shadow. The answer here is to experiment, using polaroids or digital, to check that the apparent focus is correct. Once you know whether you need to make an allowance and how much adjustment is needed, the problem will be solved.
Measuring exposure
Unless you use a handheld meter, pictures taken outdoors are normally measured using reflected light - the camera meter measures the light reflected from the subject and either tells you what it finds or tells the camera what it finds. Reflected light measurement can also be used with studio lighting (in fact you can even use a camera meter if you are using tungsten (hotlight) lighting, but for most subjects it's far better to use incident light measurement.
Incident light is the light that actually reaches the subject, not light that's reflected from it, so the measurement takes no account of the lightness or darkness of the subject and the subject is therefore more likely to be measured accurately. If you are using flash, you need a flash meter - there is simply no way of getting the exposure right without one. To find out the correct exposure you simply place the meter as close to the subject as possible and take a reading, with the meter pointed straight at the camera. Some people believe that the meter should be pointed at the key light and not the camera, and there is something to be said for this, and some people believe that the meter should be pointed partly at the camera and partly at the key light, and there is even more to be said for this argument, but I prefer to meter back to the camera. It gives very consistent results, and takes some account of the cos factor, which in effect is the light loss caused by light striking the subject at an angle, leaving it at the same angle and not reaching the camera.
Let's assume for the moment that the meter reads f11. Does this mean that if you now set the camera aperture at f11 and the shutter speed to whatever it will synchronise at that your picture will be OK? More or less, yes. If your subject is very dark it may need up to 1 stop more light than indicated, and the opposite applies for white or almost white subjects, but generally the OVERALL exposure will be right - but there's more to it than that, because this reading will not tell you the individual effect of the various lights. To find out the relative brightness, first take the reading with the meter pointed directly at your key light. Let's say this reads f11. Now take a reading pointing the meter directly at each light in turn. Let's say that the fill light reads f8 and the backlight reads f22. This tells you that the shadow area, lit by the fill, is getting half the light of the area lit by the key light and that the part of the subject caught by the backlight is getting 4 times as much as the key light. The overall lighting contrast is x8, or 3 stops. Experience with a particular type of subject will tell you whether that is likely to work for you. This method doesn't always work well for hair light, which is in effect a backlight because it is usually placed above and behind the head. The reason for this is probably because, although experience tells us how much backlighting is needed for most subjects, hair varies tremendously in thickness, colour and reflectivity. I'll never forget that I once photographed a black woman who had permed, dyed hair. If her hair had been in its natural afro style I would probably had got the hair light about right, but I wrongly assumed that because it was lighter it needed less light. The hair came out looking completely dead because it completely absorbed all the light I threw at it - and I gave it 4 stops more than the key light!
By contrast, a blond white woman would probably have only needed 1/2 stop more light than the key light. The answer here was to take a REFLECTED light reading from both the face and the hair, and to make a judgement based on that! Oh well, we all make mistakes....
Exposure for the background
Whether you are shooting in black & white or colour, forget the colour for the moment and think in terms of tone, not colour. To get the true tone of the background all you need to do is to take an incident reading from the background to the camera, and adjust the lighting on the background to give exactly the reading as the reading from the subject to the camera - it's that simple! To make the background lighter in the photo than it really is, increase the power of the background lighting by, as a starting point, 1/2 - 1 stop or, to make it darker, simply use less light.
Just how important is accurate metering? Well, if you're shooting with black & white or colour negative film there is a certain amount of latitude, or room for error, but with slide film there is very little and even small errors will be obvious. The latitude with digital cameras is about the same as with slide film, and the exposure needs to be spot on - yes, I know that you can make adjustments on your computer, but these adjustments will not turn a badly exposed image into a good one!
Lighting the background
PORTRAIT LIGHTING
A lot of people seem to have difficulty lighting the background but it really isn't difficult - once you know how. The first important point is that the background and the subject are separate and should be lit separately, if at all possible. Secondly, it's far easier to light the background well if you have a lot of space between the subject and the background. In an ideal world, 10' is probably the minimum 'easy' distance but I appreciate that for many people that amount of space is a luxury.
Do you want to light the background?
If you have the background far enough behind your subject for neither light nor shadows to spill onto it, you can probably get a mid grey tone simply by using a plain white background.... take an incident light reading from the background to the camera, and if it reads about 2 stops less than your subject, it will record 2 stops darker - about mid grey!
If you do want to light the background, there are a couple of ways of doing it. If you have only 1 light available for the background you should normally try to place it centrally. It can be directly behind and hidden by your subject, either at low level or high up (each will have its own unique effect) or, if you are using a paper roll background and you have lots of space behind it and plenty of flash power, you can place your light behind the background and shining through it. If you use this method you need to take a reflected light reading from the background. If however the background is lit by the more conventional method of reflected light, you measure the effect by an incident reading. Whichever method you use, some light will spill onto your subject and will provide a degree of backlight. If you want to achieve a pure white background you simply overexpose the background, perhaps by 1 or 2 stops. (The greater the degree of over-exposure, the less apparent any unevenness in the lighting will be but the greater the over-exposure, the greater the backlighting, and the risk of excessive backlighting degrading the edges of your subject, especially hair).
Using 2 background lights
If you have 2 lights available for the background you simply arrange them behind and to each side of your subject, pointing at an angle on to the background. Arranged with care, this method can produce very even lighting. Some manufacturers produce special angled reflectors to make this easier.
Colouring the background
This is easy. Simply fit a lighting gel over each background light. To get the original tone or colour, simply set the power to match that of the exposure needed by the subject. If you over-expose the coloured background it will come out both lighter and in a weaker shade. Of course, you can use lighting gels to light your subject too - the same principles apply.
LIGHTING THE BACKGROUND FOR STILL LIFE
Although many lighting techniques are similar for both portraits and still life, background lighting is not, and this section will hopefully make this fairly complex part of the job a little easier. Professionals use methods and equipment which is beyond the reach of most amateur photographers. This section ignores professional background lighting techniques, but I will mention one professional technique that anyone can achieve with home-made equipment.
Floating on air is a useful technique, and involves using and lighting a background that becomes invisible in the final photo.
Simply make a wooden L-shaped frame, (a bit like a chair frame without the seat and back) and cover it with a 'sweep' of plastic material, preferably diffused. If you don't have diffused material you can use clear plastic but will need to fit a diffuser, such as tracing paper, to the underside. All you need to do to light it is to place a light underneath and set the power as required. If the lighting level is too low the background will not be illuminated evenly. If you set the level too high, the edges of your subject will be degraded. If you get it just right however you can have a pure-colour background and the background can even show shadows if required. If, because of cross-lighting, your subject is throwing the dreaded double shadows you can set your under-lighting high enough to get rid of the second shadow but whilst leaving the main shadow. You can change the colour of your background by using lighting gels
But why bother when you can take the background out in Photoshop? Well, if you believe that Photoshop can replace good photography.... my own view is that Photoshop should be used to make good images better, not to rescue bad ones, and it's always better and usually much quicker to get the lighting right in camera than to try to put it right later.
Other ways of lighting the background
It's very difficult to light the background easily unless you use the method described above. If you use a 'scoop' background there will always be some unevenness because either the base or the back will receive more light, and the curve of the scoop is particularly difficult to light evenly. If you use a separate base and back, you can leave a large gap between the two and light each individually, with the light for the back coming up from underneath and shining through the gap, but it isn't easy to get it right.
Another method is to place a light behind the background and shining through it, with another light above and behind the base. This will both backlight your subject and illuminate the base.
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Garry Edwards is a commercial photographer who also provides training courses in studio photography to both amateur and professional photographers. Please click here for details of his courses (www.commercialphotography1.co.uk/courses.htm).
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