Set Lighting Technician's Handbook: Film Lighting Equipment, Practice, and Electrical Distribution

by Harry Box

When reading the output of individual lights, some cinematographers replace the hemispherical collector with a flat disk collector. The flat disk reads only light coming from the front. The disk is also used when photographing flat artwork, such as a painting or front-lit titles.

If you use a high-wattage light and place it far from the action, the light level will be relatively even from

one side of the acting space to the other. If you use a lower-wattage light source and place it close to the actor, the light level will fall off quickly on the objects surrounding the actor.

Materials like Rosco scrim and bobbinet fabric are black woven materials, which the grip department typically keeps on hand as a quick way to dim down a too-bright neon or

Lights can be mounted to a crane or dolly or handheld by a lighting technician to make the light move. Reflecting a PAR 64 into broken mirror fragments in a shiny silver tray of water creates lively water striations.

Although the main purpose of an egg crate is to contain the light, on larger frames it also tends to even out the brightness of the light as you move toward the light source. As you move closer to the light source, the fabric cells occlude progressively more of the diffusion surface. The egg crate effectively reduces the exposure range in the acting space by reducing the rapid increase of brightness, what DPs like to call sourceyness. Close to the source, the egg crate opposes the inverse square law.

When you go closer to an egg crate, it starts to block the light from the sides, reducing brightness on the talent and therefore opposing the inverse square law

We have transitioned to a new mode of operation where the dimmer is simply dialed up or down as needed, and the consequence is often that LEDs are used at very low dimmer settings. There are notable downsides to this. Most manufacturers will tell you, below 10 percent on the dimmer, color becomes very challenging to manage. The manufacturer’s advertised color rendering measurements are taken at the light’s optimal performance, at 100 percent. Maintaining color quality at low dim levels is complex because dimming changes the temperature, which affects different color LEDs at different rates (among other factors). In addition, if you are operating a light only in the bottom third of its dimmable range, you are left with one-third of the dimmer resolution. Fades cannot be as smooth and can appear quite abrupt. With some LEDs you can improve the smoothness of fades by selecting different control parameters (16-bit dimming rather than 8-bit, Low End Mode, exponential or S-curve dimming law), but it may be a better idea to set the light at a higher dimmer setting and compensate by using thicker diffusion, or cover the face of the light with ND gel or a double layer of bobbinet, for example. Dimming out to zero is a challenge for many LED controllers. They tend to blink out once they get close to zero. This is a product of how the dimming circuitry is arranged. For more about LED dimming and possible flicker issues see Chapter 21.