The Profile fixture is the most common and most powerful of the array of fixtures available to the lighting designer. It is also sometimes called a Leko (the Strand Leko was a popular fixture in the 70s and 80s and this has in some places become the generic name for an ERS).
In many ways, the Profile fixture is the Swiss-army knife of lighting fixtures. All Profile fixtures, regardless of manufacturer, have a few things in common:
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The profile fixture was born as the conventional Ellipsoidal Reflector Spotlight, hence the fixture's tendency to be called an Ellipsoidal or an ERS. The unique optics of this type of fixture allowed for an extremely precise beam of light that could be shaped by manipulating the light at a specific point in the path between the reflector and the lens. This point is the gate (see diagram to the right). This is where the shutters and the slot for accessories such as gobos reside.
These fixtures utilize a tungsten/halogen lamp, the reflector bounce the light towards a pair of lenses which refined the beam into a repeatable specific angle of output, creating a predictable field of light at any point along the path. This diagram of an ERS shows all of the inner workings of the instrument. The 'Focus Knob' loosens up the lens tube to change the relationship of the lenses and the lamp. Much like focusing a camera, this either sharpens or fuzzes out the edge of the beam. The shutters and the template (gobo) slot are right next to each other, because this is the place within the optics that allows a very sharp focused edge. Color media is placed in the gel frame in front of the lens. While much of the industry is moving towards LED fixtures, especially for new construction, there are many venues that continue to use lamp-based conventional fixtures. Diagram from: technical information for Harvard's Loeb Drama Center: link |
The optics of the LED Profile fixture are similar, but the tungsten/halogen lamp has been replaced by a powerful array of LED chips, carefully positioned so that the light that is emitted from the fixture keeps the properties of the old conventional Ellipsoidals. The instruments often have multiple color engines, reducing or eliminating the need for colored gel. The LED fixtures also use much less power than conventional fixtures: 575w or 750w were typical for a conventional lamp, and older fixtures regularly were lamped at 1000w or more. LED profile fixtures can get comparable brightness from fixtures using 300w.
These fixtures are controlled much like automated fixtures. The fixture itself is assigned a DMX address, and then the on-board computer controls any additional parameters. An LED Profile fixture could have as few as one parameter, such as the Source 4WRD LED retrofit fixture (DMX only controls the intensity of the single color LED lamp), or as many as 12 or 18 for fixtures that have multiple color LEDs, fans, strobe control, and other intensity based effects.
These fixtures are controlled much like automated fixtures. The fixture itself is assigned a DMX address, and then the on-board computer controls any additional parameters. An LED Profile fixture could have as few as one parameter, such as the Source 4WRD LED retrofit fixture (DMX only controls the intensity of the single color LED lamp), or as many as 12 or 18 for fixtures that have multiple color LEDs, fans, strobe control, and other intensity based effects.
Fixed Angle ProfileThe Fixed-Angle profile fixture is an instrument that utilizes interchangeable lenses to adjust the angle of light coming from the fixture. The designer chooses where the fixture hangs in the rig, and then based on the throw distance, or the distance between the fixture and where the light lands, chooses the lens with the beam angle to best achieve the desired result.
If the designer is looking for a 10 foot diameter pool of light on the stage, a light that is hanging closer to the stage will need a wider beam angle than a fixture hanging farther away. |
Lens Tube or 'Barrel'Modern fixed angle Ellipsoidals have the ability to change the angle of the light simply by swapping out the lens tube. Usually, the angle is on a decal on the side of the lens tube, and the most common angle lenses are 50°, 36°/40°, 26°/30° and 19°/20°. This is a rough approximation of the field angle. See the Photometrics section for more specific information on this.
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Long Throw ProfileIt seems counter-intuitive that in order to get a narrower beam the light would need this massive lens assembly- but that's how the physics work. A 5° lens assembly will create a 10' pool of light from a distance of about 70'.
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Zoom ERSZoom Spotlights allow on site adjustment of the field angle without the need to swap out lenses. By adjusting the position of the lenses, the instrument can be focused anywhere within a given range. Manufacturers often design zoom fixtures in 'far throw' and 'near throw' versions. The far throw fixtures that I have come across adjust between 15° to 35°, and the near throw fixtures go from 30°-55°.
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PhotometricsPhotometrics are the measurable aspects of light. In short, how big is the pool of light, and how bright is it? When the designer is choosing lights for the design, it is important to know that the instruments will do what they need to do. Go to the Photometrics page to learn more about the science of measuring light output.
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GobosA Gobo is a steel or glass template that is placed in the gate of the unit. By running the edge of the beam sharp or soft, the designer either gets a very specific pattern of light and shadow, or a fuzzy breakup of the light. More details on the Gobo page.
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Because of how the optics work inside the instrument, when gobos and shutters are used, they appear in a 'mirror image' when they finally come out of the instrument. For instance, when you push in the shutter on the physical bottom of the lighting fixture, the top of the beam of light is cut off on the stage. Gobos that have a specific 'up' and 'down' orientation must be installed 'upside down' into the instrument in order to project correctly on the stage.
Modern ERS lighting instruments also have the ability to 'rotate the barrel' or twist the gate and lens tube in either direction. Sometimes the angle at which the light is hung does not allow the electrician to make the angle shutter cut that is necessary. In this case, rotating the entire lens tube (including the 'gate') will allow the proper cut to be made. This also helps when trying to get a gobo to properly line up. |
Additional InfoSome instrument manufacturers:
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