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Physics of Stage Lighting

When it comes to stage lighting, various theories of physics come into play. A professional will look at the theory of reflection, angle of incidence and interaction of light with various surfaces. Based on these, the professional will try to judge how a stage lighting beam will behave when it is allowed to fly. Today, stage lighting is done after taking into consideration various surfaces, such as PVC wall coverings, Perspex plinths, glass, wood and paint and cloth finishes. Getting the stage lighting right can be cumbersome if the physics of stage lighting is not taken into consideration.

Light Diffusing Material
- A surface covered with a light diffusing material, such as felt, throws light in various directions due to its bumpy nature. As the surface is not grainy like velor or suede, this diffusing material gives a similar effect to the viewers from all angles. The light reflects off the bumpy sides of the surface and goes straight into the eyes. This is termed as diffusion reflection. Since the light pings around and the surface shoots off light at different angles, the viewers get a pretty even view of the surface. Hence, light diffusing materials are always preferred by stage lighting professionals.
Shiny Surface
- The reflective nature of high gloss or shiny surfaces, such as PVC-based fabrics, is quite high. Since these surfaces are flat and less bumpy, there is less diffusion of light. However, they diffuse color and produce specular reflection. Any photon that hits a shiny surface is pinged off straight, depending on its originating source, producing an impression like the window shape reflection.
Angle of Incidence and Reflection
- What makes shiny surfaces less diffusing? The answer concerns the concept of angle of incidence -- an angle between where a light source strikes and the surface Normal. A 30-degree lighting angle bounces back to the other side of the surface Normal, if it is also at 30 degrees. This is helpful in setting up mirror effects when doing stage lighting.
Lighting Positions and Angles
- Focus on how light behaves once it is released. Know the difference between specular and diffuse reflection, understand angle of incidence, lighting positions and color mixing fixtures and try to use this knowledge while trying to decide lighting positions and angles. Also offer the set production in-charge designing suggestions by stressing on the importance of using the right set material that can reflect light properly to the viewers.

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