I and others have posted so often about not positioning two lights, one either side of a subject, that I thought that it might be useful to describe a good starting point for lighting single people.
The problem with having one light either side of the subject on equal power is that you end up with shadows falling in both directions across the face. Even if they are only subtle the effect is often to make a face look unnaturally bulgy or blotchy. Strangely, at the same time you can end up with light which is incredibly flat - it has no apparent direction and no significant falloff - which can make folk look even more 2d than normal in a photo.
The effect still happens if the lights are on different power settings.
There are circumstances under which it can work but it’s generally best avoided. As
@Phil V says.. there’s only one sun.
Please bear in mind that this is (a) my take and (b) just a starting point – do adjust to your personal taste.
One light
A good place to start is to have a modifier about the same size as your subject, about that distance from the subject, with the bottom edge of it in line with the subject’s forehead. To finish Phil’s quote.. there’s only one sun and it’s above us.
e.g. if you are doing a head and shoulders shot then a 60cm softbox about 60cm from the subject would be fine. You can place it directly in front of your subject, completely at the side or somewhere in between. There's nothing wrong with having the light square on to your subject. If it's close and high enough then you will still get nice 3 dimensionality; you don't
have to position it to one side for that.
Consider angling the light downwards or sideways (aka ‘feathering’) so that any hotspot strikes the chest rather than the forehead. This is especially important with shoot through brollies.
Generally you want to have the nose shadow to have a soft edge and for it to be falling downwards towards the mouth but not actually touching the mouth. Some people position things to ensure that there is a catch light visible in the subject’s eyes but I reckon the nose shadow is more important.
The same is true for someone lying down; position the light above the forehead relative to the subject.
Reflectors
If the shadow under the chin is too dark then use a white reflector under the chin and in line with the light. Don’t bend it; just keep it flat. It’ll probably need to be closer than you think. If it’s having no effect than check the angle of the reflector, and make sure that the light is actually hitting it. Just check that you don't accidentally over-light the underside of the nose.
If the light is on one side of the frame and the other side is too dark then add a large white reflector directly to the side. That’ll gently lift all the shadows evenly with nicer results than adding a small second light.
Fill light
If the whole image is too contrasty or the shadows too dark then you can consider adding a second light. This fill light should be as large as possible and
directly in line with the camera position. Bouncing a flash off a white wall works well. If you can’t bounce the flash then try a large softbox or umbrella – but be careful you don’t introduce a second set of shadows. You may need to position it quite high and point it downwards. Start with the fill light on minimum power and increase gradually.
Accent lights
Additional lights are often used as accents to the main (key) light to help separate the subject from the background, lighting the subject from behind their position. The use of accents should generally be subtle. Gridded reflectors or stripboxes work well for this – watch for light entering the lens directly and causing flare. It can be really nice to catch the jawline with a slight highlight.
An accent light directly opposite the key light tends to increase drama but can look unnatural and make someone look ‘cut out’. This is especially true when the accent is the sun; it usually works best to have the sun and the key light towards the same side of the subject.
If you feel the urge then you can add accent lights on both sides of the subject and a hair light from above. It’s tricky to keep everything looking natural though.
Background lights
It’s quite common to pop a splash of light or colour on the background behind the subject, or to create a gradient. Gridded reflectors work well for this too. Again be careful, it’s easy to create something with a bit of an old fashioned 80s vibe
There’s an awful lot more which could be said on this subject – including some cases where one light either side of the subject does work – but the above is a good starting point for the great majority of lit portraiture.
I hope this is of use. I may get around to adding some diagrams and sample pictures one day. And if you think I've made a mistake, omitted something important or just been confusing do let me know; I'm quite happy to edit this.
