Where to put your light when you only have one

Most people buy the light before they decide where it goes. That is the wrong way round, and it is an expensive habit, because the position is free and the lamp is not. A single light in the right place will make you look like someone who films for a living. The same light, sitting on your desk pointing straight at your face, will make you look like you are being interviewed about a crime.

The difference between those two results is roughly a metre of floor and about forty-five degrees of arc. Here is how to find it.

Exposure and shape

A light helps the camera record the subject and shapes how it appears. For a face, watch the balance of light and shadow as you move it.

Shape comes from shadow. A face lit from directly in front has no shadow anywhere, so it reads as flat, and flat reads as cheap, because it is what a webcam does. A face lit from one side has a bright side and a shaded side, and the line where one becomes the other is what makes a nose look like a nose. That line is the whole point of the exercise.

Check both exposure and where the shadow falls.

Where does the light go?

Three numbers, and none of them is a rule so much as a starting point you will move once you see yourself.

The angle: about forty-five degrees off centre

Stand where you will sit. Put the camera in front of you. Now move the light out to one side until it is roughly halfway between the camera and your shoulder. You are looking for a shadow from your nose that falls diagonally down towards the corner of your mouth on the other side, and stops before it gets there.

If the shadow reaches across your cheek and off the far side of your face, you have gone too far round. If there is no shadow at all, you have not gone far enough.

Which side? Whichever one your room allows. If you have a window, put the lamp on the same side as the window rather than fighting it. Two light sources arguing from opposite sides is one of the most common ways a home setup starts to look strange, and nobody can ever say why.

The height: above your eyeline, tilted down

Light from below is the torch under the chin, and your face knows it even if your conscious mind does not. Raise the lamp until it is higher than your eyes and angle it down towards you.

Not much higher. If the light is directly overhead you will get shadows in your eye sockets and under your nose, which reads as tired. Somewhere around the top of your head, looking down at you, is enough.

The distance: closer than you think, then diffused

Moving a light closer increases its apparent size and can soften the shadow. Use a diffuser or softbox suitable for the fixture, following its heat and clearance guidance. Judge the result from the subject's position.

This is the one place a small purchase helps, and it is a diffuser rather than a brighter lamp.

What if the light has to be behind the camera?

Sometimes the room decides. A narrow office, a kitchen counter, a corner you cannot move out of.

In that case, accept the flatness and buy back the shape somewhere else. Move yourself further from the wall behind you: as long as your light stays close to you rather than moving back with the wall, the wall now sits much further from it and falls darker on its own, so you separate from the background by contrast instead of by shadow. Turn on a lamp in the background, well out of your eyeline, so there is something with depth behind your head. Both of these cost nothing and both of them do part of the job the missing angle was doing.

Do you need a second light?

Only if the setup or the look needs it.

The second light is not there to make you brighter overall. It lifts the shadow side, adding a little light where the first one left dark, so the dark half of your face keeps some detail instead of going black. That lowers the contrast between the two sides; it does not change how hard or soft the shadow edge is, which is set by the size of the light, and only that. It is a real improvement and the smallest of the three. Established practice is to run it noticeably dimmer than the first one, judged by eye rather than by a ratio, because a fill that matches the key cancels the shape you just spent an afternoon creating.

Before you buy one, try a white wall, a piece of foam board or a sheet on a chair, placed on the shadow side to bounce a little of your existing light back. It does the same job for nothing, and it will tell you whether you wanted a fill light or whether you wanted your key light moved.

Start with the angle

In order, and stop when it looks right:

1. Try the light at about forty-five degrees. 2. Raise it above your eyeline and tilt it down. 3. Adjust distance and suitable diffusion. 4. Check separation from the background. 5. Add another light only where it has a job.

The first four are free. If you film weekly, do them once, mark the floor with tape, and stop thinking about it.

Where this stops being a lamp position

There is a point at which lighting stops being geometry and starts being a decision about what the video is for. A cook needs the hob lit as carefully as the face, because the hob is the lesson. A piano teacher needs the hands lit brighter than the room, because the hands are what people came for. On one music education partnership the fix was not a better camera, it was artificial light balanced specifically on the angle covering the fingers, because the fingers were the thing being taught.

That is the question worth asking before you buy anything: what is the one thing in this frame the viewer must be able to see? Light that, and let the rest of the room fall where it wants.

Sources and evidence

What here is established lighting physics, and what is our own starting position for a single light.

What is established. ARRI's own lighting handbook states that the quality of light produced by an instrument, hard or soft, is set by the physical size of the source and not its intensity, which is the basis for treating distance and diffusion, not brightness, as the way to soften a face. The inverse-square law, formally defined by the CIE, describes how a light's effect on a surface falls away with the square of the distance travelled, the physical reason a light kept close to the subject lets a background wall sit far enough from it to fall darker on its own. Roger Deakins' own lighting forum is a working illustration that a single well-placed light, without the rest of the diagram, is a legitimate professional starting point rather than an exception to a rule.

Our method. Setting the angle, then the height, then the distance and diffusion, and only after that considering a second light or moving away from the wall, is this studio's own order of cheap fixes, not the only order that works.

References.

• ARRI (Arnold & Richter Cine Technik); author Bill Holshevnikoff. ARRI Lighting Handbook, Fourth Edition. arri.com. Shadow hardness/softness is set by the physical size of the light source relative to the subject, not its brightness. Used in the two lighting pieces and the talking-to-camera piece. Text dates to 2016 (fourth edition); general lighting theory, not a claim about any specific fixture.
• International Commission on Illumination (CIE). 17-25-105 'photometric inverse square law', CIE S 017:2020 International Lighting Vocabulary (e-ILV). cie.co.at. Inverse-square falloff of light with distance; used to explain background separation and why a background darkens. Used in background-and-atmosphere-lights and the lighting pieces. Formal definition only, a special case of the wider photometric distance law; gives no production guidance itself.