Framing Shutters are an integral part of every lighting designer's toolkit. They are found on both conventional and automated lights and serve important purposes. Generally shutters are used to block out light from unwanted areas. Through the use of four variable blades, the light output can be cropped to only certain areas or specific shapes. Shutters are often used to eliminate lighting spill onto set pieces and other elements that need to remain dark. Moving a shutter into a masking position is typically referred to as a "shutter cut."
The most common use of shutters within conventional lighting can be found in ellipsoidal spotlights such as the Martin ELP Ellipsoidal fixtures. As with most functions on conventional fixtures, the four shutter blades are manually moved into various positions. In addition, the user can rotate the barrel to achieve different "off-axis" angles with the shutters. Some ellipsoidals even feature locking mechanisms to ensure the shutter cuts remain once set. By adjusting the lens focus or using frost gels, the edge of the shutter may be hard or soft.
Automated lights such as the Martin MAC Encore Performance and Martin MAC Viper Performance utilize a complex system of motors to provide remote movement of shutter blades. In addition, the entire shuttering mechanism can rotate to provide a similar effect to rotating the barrel on an ellipsoidal. As the pan and tilt of the fixture can change from cue to cue, so too can the framing shutter settings. It is extremely important that the shutter system and its software allow for tremendously accurate positioning of the blades.
Shutter blades can also be found in some automated wash fixtures such as the Martin MAC Encore Wash and the Martin MAC Viper Wash DX. The principle is the same, where the shutter blades will cut off light output from particular areas. However, since the fixtures are wash functions and employ Fresnel or other soft lens abilities, the sharp cutoff is of the shutter will appear more subtle.
An additional function with automated framing shutters is the ability to create dynamic movement effects by continuously changing the framing shutter settings. This can result is some very exciting looks from the fixture as the shape of the output light constantly morphs into new shapes.
Blocking the Light
Framing shutters have been an important tool for lighting designers for many years and will continue long into the future. Eventually we will see digital shutters that allow for any shape (or mask) that one desires. Until then, conventional and automated fixtures will continue to use metal blades to shape the output and eliminate light from unwanted areas.