Can you light a background with just one light?

Can you light a background with just one light?

Can you light a background with just one light?


Yes, but it isn’t a perfect solution. The video above shows the basic approach to lighting a white background with a minimum of two lights, and if you’re forced to produce a white background shot with just one light then the same basic principles apply, but more care is needed and some little tweaks are needed too…

Overexposed, single light

Overexposed, single light

What a lot of people do is to simply use more lighting power on the background, and that is 100% the wrong approach.
Using more power, so that the whole of the background ends up overexposed to the point where it’s completely white, involves having the area directly lit by that single light so badly overexposed that an excessive amount of light travels back towards the camera.

This has two negative effects:

  1. So much light hits the rear of the subject that fine edge detail, such as skin, hair and light clothing, is destroyed
  2. So much light hits the lens that lens flare is created, and overall contrast is severely reduced.

The photo on the left shows the result, all of the fine detail from my model’s hair has been destroyed – and that’s before I’ve actually added the light needed to photograph her – in the shot you see here, it’s just the background that has been lit, the light that is also hitting my model is just light that’s bounced off of the background. By the time light is added to her face, the situation will be even worse.

So, how should it be done?
There are a couple of ways that work fairly well, although no method involving a single light source on the background can ever produce perfect results.

 

Hide the flash head directly behind the subject. The advantage of this method is that if the light is directly behind the subject and pointing straight at the background, white_002_blogit will light the area immediately behind her adequately, leaving only the white areas that will either be out of shot or at least well away from her, darker than we want them to be. This isn’t always practicable of course, when a model is moving around on the set, changing poses, some shots are bound to show the flash head or the lighting stand in the shot, and with some shoots the subject just may not be big enough to prevent the light from showing – but it’s a good approach when the situation allows.
A variation on this is to mount the light on a boom arm behind and above her, and to aim the flash so that the area immediately behind her is lit, this still isn’t perfect but it does make life easier, if you have a boom arm.

Another approach, which works if it’s just a head shot or similar, is to mount the light on a floor stand, again with the flash aimed at the area directly behind her. Whether you use a boom arm or a floor stand though, the light will be hitting the background at a fairly acute angle, which isn’t ideal.

Position the light off the the side and aimed at the area directly behind the subject.
This is easier than having the light directly behind the subject because it doesn’t rely on the model hiding it with her body, but again the light is hitting the background from an angle.

When the light strikes the background at an angle, much of the light is lost as far as we are concerned, because it bounces off into the ether, instead of bouncing towards the camera. This isn’t a problem in itself but it does mean that a more powerful flash head is needed than if the light is hitting the background square-on.

Regardless of exactly how you light the background and how many lights you use for the job, the golden rule here is to use as little power as you can possibly get away with on the background lights, to avoid creating lens flare, to avoid degrading fine edge detail and to avoid creating unnecessary light wrap. Various tutorials and videos that advocate overexposing the background by about two stops are in fact talking nonsense, this amount of overexposure causes the problems that we need to avoid!

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Only expose for the area immediately behind your subject, use blinkies to get it right

The necessary amount of overexposure, when shooting on digital, is in fact just 0.7 (or 2/3rds) of a stop, it’s all that’s needed and is also the highest level of overexposure that produces reasonable results.

Use your blinkies to get the exposure right
Enable the blinkies on your camera, so that the overexposed areas on the shot blink at you when you view the shot. As long as the area immediately behind your subject is overexposed and blinking at you, you have enough over-exposure to do the job.
Of course, the areas that are not blinking will photograph as grey, but that is what you should be aiming for, all that you then need to do is to lighten those areas in PP, which is a very quick and simple job.