Conventional fixtures (aka. Incandescent Fixtures) are lighting tools housing a lamp, usually some kind of reflector, and lenses. Their light output is regulated by a dimmer.
Conventionals differ from practicals mainly by purpose. Practicals are meant to be shown on stage and have a working light representing physical lights on stage, such as a hospital surgery light that is both a set piece seen by the audience, and that must be electrical while conventionals project a beam of light, without the body of the fixture being seen. This cam get quite blurry on a show where actual conventionals are used as practicals.
Below we will look at the common parts of conventional lights, as well as look at common lights, ranging from the least amount of control of their beam, to most.
Parts of the lights
Every conventional fixture has different uses in a lighting package, yet there are many overlaps in their parts.
- This refers to the electrical connection for the dimmed power. See the power cables page for more information on the various electrical connectors tails can have.
- What normal people would call a "bulb" The part usually made of glass where a filament is housed, that when voltage passes through it, will create light. Lamps come in a wide range of wattages, affecting both the light and heat output of the fixture. In some fixtures like Pars (as discussed below) the lamp may be a multi part of the fixture.
- Since most conventional lights wish to direct the light output in a certain direction, conventionals have either glass or metallic pieces that reflect the light beam in a certain direction within the fixture. Common reflector types include Parabolic Aluminized Reflectors, which give us the PAR fixtures below, or Ellipsoidal Reflector Spotlight, ERS, also below.
- Possibly the most direct influence to the shape of the light beam aside from the reflector, Lenses are usually adjustable, to help make the light perfect. How they are changed varies from fixture to fixture.
- A bit more variable, from an extra accessory, to a built in feature, shutters help control the shaping of the light, allowing part of the fixture's output to be cut off elements of the stage that it would not be desirable to light, often times masking or set pieces.
Cyc lighting is usually used to light a backdrop called a Cyclorama. It can provide a wash on scenery up to 25ft tall. Cyc lighting can be from a ground, then called a ground row, or from a batten. Since Cyc lights are trying to cover a wide area, they have no method for controlling the shape or size of the beam.
While most cycs are powerful lamps, usually in the range of 500 Watts and up, some smaller versions use MR16 lamps instead.
Cycs are built into fixtures of either 3 Cell or 4 Cell units, allowing some color mixing upon the cyc. Modern Cyc lights are intelligent LED fixtures allowing mixing from the console.
There are 2 main types of strip lights, one is often a practical, The other is a conventional.
The practical variant comes in 2 further types, LED or incandescent. The incandescent is often seen on marquees, blinking in patterns, or mounted to set pieces to recreate a similar effect. The number of Circuits on these lights vary. The number of circuits can change how the strip lights are used.
The LED variant is vary similar, but much smaller. These lights highlight, and can be either a single color, or controlled by an LED Driver, allowing color changing.
Parabolic Aluminized Reflector Light (aka PAR)
A type of electric lamp that is mostly used in theater, concerts, and motion pictures. The sealed beam light produces an intense oval pool of light with unfocused edges. These types of lights come in various diameters, the number indicates diameter of the housing unit. It is common to fit these lights with various color gels and use them to wash the stage in color. Pars have a single reflector, and a single lens to disperse the light beam. These lenses are in a variety of sizes. These usually are not numerically described, but with more descriptive terms, such as "Very narrow, Wide Flood" etc.
Shaping the beam can be controlled by using different lenses to adjust the size of the pool, as well as using either barndoors or flags to cut the light from hitting undesired objects.
Fresnels are vary similar to par fixtures. They both produce beams of light with an even distribution, and both can only be shaped with barn doors or flags. Fresnels, have one cheife advantage though. While a par needs to have it's lenses changed to alter the size of the beam from the fixture, frenels are designed to change the beam size by altering the distance between the lamp and the special fresnel lens.
Ellipsoidal Reflector Spotlight (aka. ERS)
A type of lighting fixture that collects and then distributes light through a lens or train of lenses, they are favored for their strong well defined lights and versatility. They have many purposes, and ways to adjust their light output.
- As the name suggests, the reflector is shaped in an elliptical arrangement. Ideally, the lamp is placed in 1 focus point and all of the reflected rays from the lamp pass through the other focus point. Because the optics are reflected rays through the focal point, any accessories used to shape the beam prior to the lens train will be reflected 180 degrees from the beam.
- Lenses change the beam spread of the spotlight, and the sharp or soft focus of the beam. In an ETC Source 4 ERS, the same body can accept a wide variety of lens barrels to change the spread, which allows the same body to be used for different throws.
- Spotlights have shutters built into their body, to shape the light beam. Since these are located in the body before the lenses, opposite shutters will cause cuts to the beam.
There are a few slang terms used for these lights. ERS, as the acronym, or Spotlight are the most common. Some people will use terms such as "leko" or manufacturer names like "Altman" "Source 4 Spot". The lights will be further described, by both lamp wattages, and beam spread.
Fixtures of this Type
- You do remember the special properties of ellipses right? if not, brush up, and pay special attention to the Foci, https://en.wikipedia.org/wiki/Ellipse#The_Normal_bisects_the_angle_between_the_lines_to_the_foci