ETC Source Four

ETC Source Four

The ETC (Electronic Theatre Controls) Source Four (also known unofficially as Source 4 or S4) is an ellipsoidal reflector spotlight, a type of spotlight used in stage lighting. The ETC Source Four revolutionized stage lighting in 1992 with the introduction of revolutionary lamp and reflector technology, invented by David Cunningham, tool-free lamp adjustment, and a rotating, interchangeable shutter barrel. The Source Four ERS is the most widely used Ellipsoidal Reflector Spotlight among professional theaters in the United States. Source Four is a registered trademark of ETC (Electronic Theatre Controls).

Glass Reflector
The Source Four is the first ERS to use a faceted borosilicate reflector behind the lamp. Nearly all stage lights have some form of reflector positioned behind the lamp to reflect otherwise wasted light out the front of the instrument. The Source Four's unusual reflector is dichroic, meaning that it reflects light of only certain wavelengths. The Source Four's reflector reflects back 95% of the visible light striking it, while allowing over 90% of the infrared radiation (heat) to pass out the back of the instrument . This produces a much cooler light which is less destructive to gobos or color gels at the front of the fixture.

Tool-free lamp adjustment
Lamp adjustment, or bench focus, is used to achieve an even field of light, and to remove hot-spots which can destroy color filters. On the Source Four, adjustment can be done without tools, and is more accurate than previous fixtures, which makes it easier than the previously common four-screw assembly that can be challenging to operate, even for many professionals. Bench focus should be periodically done with all theatrical fixtures to ensure maximum output and field evenness and to improve color filter life.

HPL lamp
The proprietary HPL (High Performance Lamp) lamp uses a compact filament, which concentrates the most light where it is efficient in an ellipsoidal reflector. At 575 watts, the HPL lamp in a Source Four produces light equivalent to a 1000 watt spotlight using previous technology. This lower amount of energy consumption saves money on electricity and creates less heat. The HPL lamp also gives the fixture its name. The lamp (light source) has 4 filament strands, hence Source Four. It is also available in 750 W and 375 W versions. HPL lamps are also available in longer life versions that reduce the color temperature from 3250 kelvins to 3050 kelvins to give the lamp a life of around 1500–2000 hours as opposed to the 300-400 hour life of the standard HPL.

HID
ETC also manufactures an HID Source Four with a metal-halide lamp. The fixture has a ballast attached to the yoke of the fixture which provides the added power required to strike and operate an HID lamp. HID lamps are not dimmable. The HID fixture offers great energy savings over the standard HPL fixture.
 

Back to Top

Barrel
A Source Four with a 10 degree lens on the front (left)
The Source Four is the first modern fixture to feature a rotating shutter barrel[10], which makes framing objects much easier regardless of lamp orientation. In previous fixtures, the shutters had only a limited range of motion and could not be rotated. The shutters are also made from stainless steel, which does not warp easily under the heat of the lamp.
ETC also offers a variety of interchangeable lens tubes with various field angles. These are: 90, 70, 50, 36, 26, 19, 14, 10, and 5 degree lens tubes, some of which are available as Enhanced Definition Lens Tubes (EDLT). The Source Four is also available as a zoom fixture, with a non-interchangeable lens tube. The metal tubes themselves have slots for many beam angles. While none of the glass lenses are common to two angles, the lens tube can be converted with the addition of new lenses. Lenses come from the factory with a painted-on dot denoting the front face. The inside of the lens tube shows which slot is for which lens.
Different field angles are better for different venues with different catwalk and electric systems[11] (and, therefore, different throws). A lens tube with a smaller field angle will light an area from far away, whereas a large beam degree such as a 90 degree can be much closer in order to light the same area. A 90 degree Source Four might be used to project a gobo from the rear only 5 feet away on a scrim at the back of the stage, while a 10 degree could be used in the back of the house, for example, in the technical booth where a technician could access it to refocus or change gobos during a show. A zoom gives the option of adjusting the field angle within a specified range without swapping the lens tube. This is helpful in the case of lighting fixtures that need to be re-focused frequently to different areas of the performing area, without having to rehang them in a different position in the lighting rig. There are two Source Four Zoom fixtures, the 15-30 degree and the 25-50 degree.

Enhanced Definition Lens Tube
In November 2005, ETC introduced the Enhanced Definition Lens Tube (EDLT). The EDLT is designed to produce images from gobos and other focus-critical instrument accessories more clearly and accurately than with the standard lens barrel. The lenses in the tube are coated with an anti-reflective material and are machined to more exact standards than the standard Source Four lens. The EDLT also increases lumen output. It is available in 19, 26, 36 and 50 degree barrels.

Third Party Offerings
Many third party companies have made accessory products specifically for the Source Four. City Theatrical manufactures a line of products that retrofit a Source Four into a tungsten source followspot[12]. Ocean Optics stepped out of the scientific industry and entered the entertainment world with their SeaChanger Color Engine that utilizes gradient dichroic disks to control color. The unit is mounted in between the source and optics and controlled via DMX[13]. Great American Market offers a special effects unit, the SX4 that is mounted in a Source Four[14] and offers a large selection of drop-in accessories that range from gobo-changers to filmFX overlapping looping gobos.

Other Source Four products
In 1995, ETC introduced the Source Four PAR which is meant to replicate the performance of PAR cans while lessening the disadvantages involved with traditional PAR cans.
In 1999, ETC introduced the Source Four PARNel as an alternative to fresnel lanterns.
In 2002, ETC introduced the Source Four MultiPAR as an alternative to striplights.
In 2004, ETC introduced the Source Four Revolution, ETC's first moving fixture. The Revolution was awarded both the EDDY and ABTT awards. The Revolution is unusual because it uses the standard incandescent Source Four lamp, as opposed to most other moving lights, which use arc lamps.

 

Back to Top