In short: This glossary covers thirty lighting terms used on set and in the studio, from the fittings and grip to the units of measure. Each entry says what the term means and how it shows up on a shoot. Terms are listed alphabetically.
Barn doors
Four hinged metal flaps fitted to the front of a light to shape and cut its beam. Use them to stop light falling where it is not wanted, such as a backdrop or the lens.
Bounce
Light reflected off a white, silver or gold surface, such as a board or a card, so that it lights the subject more softly. Bounce is often the simplest way to lift shadows. A coloured surface adds a colour cast, so check it on the monitor.
C-stand
A folding stand with a weighted base and a vertical column, used to hold flags, reflectors, lights and other grip. Each arm has a load rating, and rigging heavy kit is a job for a competent person who assesses the actual set.
Colour temperature
A way of describing how warm or cool a light looks, measured in kelvin against a theoretical glowing body. Tungsten lamps are about 3,200 K and daylight film was calibrated to 5,600 K. A mismatch between sources shows as a colour cast on camera.
Cookie
A cut-out placed in front of a light to throw a pattern, such as the shadow of a window frame or leaves. It is also called a cucoloris, and it is used to break up light on a wall or a backdrop.
Diffuser
A translucent material placed in front of a light to soften it and spread it over a larger area. A bigger diffuser gives softer light but takes output away. Some diffusion shifts the colour slightly, so check the picture.
Dimmer
A device that lowers the power going to a lamp, so the output drops. LED fixtures are often dimmed over a control protocol instead. Dimming can warm the colour of some lamps, so set the level on camera rather than by eye.
DMX universe
A block of control channels carried down one DMX line, which a lighting desk uses to set each fixture. The White Space has two DMX universes, which gives a large rig a second block of channels.
f-number
The focal length of a lens divided by the diameter of its opening, written as f/2.8 or f/8. A smaller number means a wider opening. It does not account for light lost in the glass, which the T-stop adds.
Fill light
A softer light that lifts the shadows made by the key light. It is usually weaker than the key and sits on the other side of the camera. Some setups use bounce in place of a separate fill.
Flag
A rigid frame with black fabric stretched over it, carried on a grip head at the end of a flag arm on a C-stand. It blocks light from part of the set or the lens. A flag is not a banner or loose cloth on a pole.
Flicker
A visible pulsing or banding in the light that appears on camera as flicker in the picture. It can come from the mains supply, from a dimmer, or from an LED fixture or wall that does not refresh cleanly against the shutter.
Foot-candle
An older imperial unit of illuminance, equal to the light from a one-candela source at one foot. One foot-candle is about 10.76 lux. You will still meet it on older spec sheets.
Fresnel
A spotlight with a stepped lens that lets the beam be spotted or flooded by moving the lamp. Fresnels give a hard, controllable light and are a common choice for a key.
Gaffer
The head of the electrical department, who plans the lighting with the director of photography and runs the rig crew. On a small shoot the gaffer may also operate the lights. Book one when the light needs planning, not only switching on.
Gel
A coloured or correction sheet placed in front of a light to change its colour or cut its output. Gels sit in frames on the front of the fixture and are the usual way to match a lamp to daylight or tungsten. They get hot, so check the frame and the fixture rating.
Gobo
A stencil placed in a light to project a shape or pattern, such as foliage, a window or a logo. Gobos are usually used in spotlights for effect rather than for the main light.
Grid
The rig of bars or trusses above the set that holds the lights. In the White Space the 8-bar grid is 4.5 metres above the floor, and fixtures hang from the bars and move along them.
Hard light
Light from a small or bare source, which gives sharp shadows with a clear edge. A bare lamp or a fresnel at full spot makes hard light. Soften it with diffusion when the look needs a gentler edge.
Inverse square law
The physical rule that light from a point source falls off with the square of the distance. Doubling the distance cuts the light on the subject to a quarter. This is why a small move of the light changes the exposure a lot.
Key light
The main light on the subject, which sets the shape and the exposure of a face or a product. The other lights are placed around it.
Kicker
A light placed behind and to one side of the subject to outline the edge and separate them from the background. It is also called a rim light or edge light. Use it sparingly, or it reads as a halo.
Lux
The SI unit of illuminance: one lumen falling on one square metre. Studios are often lit to somewhere around 1,000 lux, roughly the level of an overcast day. Use it to measure the light on the subject rather than the light leaving the fixture.
Practical
A light that is part of the set and seen in shot, such as a table lamp, a bulb in a fitting or a screen. Practicals often need a light of their own behind them, so they look lit on camera.
Scrim
A fine mesh placed in front of a light to reduce its output without changing the colour. A scrim is a quick way to take a little light off a fixture without moving it.
Shutter angle
The part of each frame interval during which the shutter is open, given in degrees. A 180-degree shutter is the normal setting and gives motion blur close to what the eye expects.
Soft light
Light from a large or diffused source, which gives gentle shadows with a soft edge. Softboxes, bounce and a cove lit broadly all make soft light. It flatters skin, but it can look flat when there is no direction to the light.
Spill
Light that falls where it is not wanted, such as a backdrop, a wall or the lens. Spill is controlled with barn doors, flags, distance and the angle of the fixture. On a green screen, spill onto the subject can break the key.
T-stop
The f-number corrected for the light the lens actually passes. Cinema lenses are marked in T-stops so that a cut between two lenses matches.
Tungsten
Warm, incandescent light at about 3,200 K. Cameras set to daylight need a correction gel or a white balance change to match tungsten, and tungsten fixtures give off a lot of heat on a set.
Sources
- Wikipedia, Inverse-square law, read 5 November 2026
- Wikipedia, Lux, read 5 November 2026
- Wikipedia, T-stop, read 5 November 2026
- Wikipedia, article on colour temperature, read 5 November 2026
- Wikipedia, Shutter angle, read 5 November 2026
Related guides
Questions we get asked
What is the difference between a key light and a fill light?
The key light is the main light on the subject and sets the shape of the face or product. The fill light is a softer, weaker light that lifts the shadows the key creates.
What does a gaffer do?
The gaffer is the head of the electrical department. They plan the lighting with the director of photography and lead the rig crew on set.
Why does a lighting term matter to a presenter?
Crews use the same words to plan the shot. If you know what a key light, a practical or a flag is, you can say what you need when you book and follow the setup on the day.
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