Reducing Light

Learn how to reduce the overall light output of a fixture.

There are a number of tools available to reduce either the overall light output from a light source, or to reduce the brightness on a particular part of the object you’re lighting.  Most gaffers will choose a light source that is slightly larger than what is needed, then reduce the brightness using one of the methods listed below.  This gives them flexibility should it become necessary to bright the light source – instead of taking the time to replace the light with a higher-wattage head, they can simple pull the scrims.

Wire Scrims

Wire scrims are circular metal meshes that, when placed in between the light and barndoors, reduce the overall brightness of the light. Every light has its own set of scrims and include:

Single Scrim
Singles reduce light by ½ an f-stop
Half Single Scrim
A single half scrim reduces the light by ½ an f-stop, but the wire mesh only covers half the open frame
Double Scrim
Doubles reduce the light by 1 f-stop
Half Double Scrim
A double half scrim reduces the light by 1 f-stop, but the wire mesh only covers half the open frame

Nets

Nets are light-reducing fabric stretched across an open rectangular frame.  Usually held in place with a C-stand, nets can be placed closer or farther from a light source, allowing a grip to isolate particular areas of the subject.  Most nets are open-ended, meaning one edge of the net has no metal support.  This allows the grip to feather the light grade by raising and lowering the open part of the net into the light, without risk of a shadow caused by the frame. Nets are available in several densities.Solids – Solids are metal frames covered with duvatyne, a light-blocking fabric.
The most common sizes for nets and solids are:  12”x18”,  18”x24”,  24”x36”
48”x48” – Also called 4’x’4’, 4×4 are among the most common-size solids, used to block large light sources such as the ambience from a window, or to block the spill onto a wall from a soft light.  4×4 floppies include an additional 4’x4’ piece of duvatyne sewn on one edge and Velcroed to the remaining three, so when opened, the effective area is 4’x8’.

 

Cutters

Cutters are long narrow solids intended to block the top and bottom of a light source, allowing a grip to focus the light onto a subject.  For example, when shooting a medium shot of an actor, use a bottom cutter to reduce the key light on the actor’s chest, and a top cutter to reduce the light off the top of the actor’s head to draw the audience’s attention to the actor’s face. Cutters are most commonly used in the following sizes: ·

10”x42” cutter,  18”x48” cutter,  24”x72” cutter

Dimmers

Dimmers are rheostats that, by varying the voltage to a light source, can reduce, by dimming the light. When using dimmers, be aware of the following:·
  • Don’t overload the dimmer – Make sure the dimmer is rated for the wattage of the light you’re using.  Dimmers on set are generally rated for 650 watts, 1000 watts or 2000 watts.
  • Be aware of the color temperature change – The more you dim a tungsten light, the warmer the color temperature becomes.  Although the effect is negligible when dimming up to 25%, further dimming will noticeably change the color of the light.
  • Not every light can be dimmed – Dimmers are generally used on tungsten lights only.  Kino-flos, HMIs, and other light sources requiring ballasts cannot be dimmed with traditional dimmers.
  • ND gels are applied over windows to reduce the brightness of the outside light without tinting it.
  • Once the gel has been measured, use a spray bottle of soap and water to help the ND gel adhere to the glass.  Use a squeegee to eliminate any bubbles.
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