Throw Distance

Overview

Throw Distance—in German simply "Wurfweite" or "Lampenabstand"—refers to the distance between the light fixture and what it illuminates: the actor's face, a wall, the floor. It is one of the first parameters a gaffer decides on when placing a lamp. Not only because the distance determines whether you have enough light on the subject, but because it simultaneously controls how soft or hard the light appears and how large the illuminated area is.

Important distinction: In the world of video and projectors, "throw" refers to the distance from the projector to the screen, often expressed as a ratio (throw ratio). In set lighting, however, it concerns the actual lamp-to-subject distance and its effect on brightness and light character.

The Inverse Square Law

Throw Distance cannot be understood without the Inverse Square Law. The brightness on the subject decreases with the square of the distance—if you double the throw distance, only a quarter of the brightness arrives, not half. Conversely, the illuminated area quadruples: what hits a small spot from one meter away covers four times the area from two meters away—but significantly darker.

This leads to a practical lever that every DoP knows: the closer the lamp is to the subject, the faster the light becomes darker towards the depth (steeper falloff). If the lamp is far away, the difference in brightness between the front and back of the image area is small—the light appears flatter and more even.

Use on Set

Throw Distance is always a compromise between three things simultaneously: brightness, light softness, and falloff. A parallel practical example—if you want soft light, you move a large, diffuse source close to the face. This makes the source relatively large and thus soft, but costs you strong falloff: if the actor moves back a step, they disappear into darkness. If you need even light across a movement, you move the lamp further away and increase the power.

Beam character plays a role: Narrowly focused spot sources work over long throw distances because they maintain their intensity within a narrow cone. Wide flood setups, on the other hand, are tools for short to medium distances because the energy is quickly distributed over a large area.

Practical Tips

• If your actor moves in depth and you don't want them to become constantly too bright or too dark: set the lamp further back and increase the power—the falloff across the movement will be flatter.
• If you need more light quickly in a confined space without getting a larger lamp: first check if you can simply move the existing source closer. Due to the inverse square law, halving the distance already provides four times the brightness.
• When lighting backgrounds, remember that the same lamp that perfectly illuminates the subject will hit the wall behind it noticeably darker depending on the distance—this can be used intentionally for depth staging.