Source Four
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The Electronic Theatre Controls (ETC) Source Four (also known unofficially as Source 4 or S4) is an
ellipsoidal reflector spotlight Ellipsoidal reflector spot (abbreviated to ERS, or colloquially ellipsoidal or ellipse) is the name for a type of stage lighting instrument, named for the ellipsoidal reflector used to collect and direct the light through a barrel that co ...
(ERS) used in
stage lighting Stage lighting is the craft of lighting as it applies to the production of theater, dance, opera, and other performance arts.
. First released in 1992, the Source Four was invented by David Cunningham and features an improved lamp and reflector compared to previous ERS designs, tool-free lamp adjustment, and a rotating, interchangeable shutter barrel. The Source Four is widely used by professional theaters across the globe.ETC , Explore the Source Four , Main
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Glass reflector

The Source Four uses a faceted
borosilicate Borosilicate glass is a type of glass with silica and boron trioxide as the main glass-forming constituents. Borosilicate glasses are known for having very low coefficients of thermal expansion (≈3 × 10−6 K−1 at 20 °C), ma ...
reflector behind the lamp. Nearly all stage lights have some form of reflector positioned behind the lamp to reflect otherwise wasted light out of the front of the instrument. The Source Four's reflector is
dichroic In optics, a dichroic material is either one which causes visible light to be split up into distinct beams of different wavelengths (colours) (not to be confused with dispersion), or one in which light rays having different polarizations are abs ...
, meaning that it reflects
light Light or visible light is electromagnetic radiation that can be perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 tera ...
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 Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from around ...
radiation (heat) to pass out the back of the instrument. This produces a much cooler light which is less destructive to
gobo Gobo may refer to: Places * Gobō, Wakayama, a city located in Wakayama Prefecture, Japan ** Gobō Station, a railway station in the city * Gobo, Cameroon, a commune in Cameroon Plants * Gobō (''Arctium lappa''), a biennial plant * Gobo (bur ...
s or
color gel Color (American English) or colour (British English) is the visual perceptual property deriving from the spectrum of light interacting with the photoreceptor cells of the eyes. Color categories and physical specifications of color are associ ...
s at the front of the fixture and reduces localized heating of the lighting target.


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 can be more accurate than older methods. The most common problem with lamp alignment is the lamp dropping too low in the reflector, causing a hot spot at the bottom of the beam, and a dark area at the top. This may be corrected by a realignment of the lamp. There are two adjustments that can be made to the cap. 1. The center screw controls the depth of the lamp into the reflector. Loosening this screw causes a spring to push the lamp further inside the reflector, creating a brighter hot spot in the beam. Tightening this screw will draw the lamp backwards, for a flatter, more even light field. 2. The wider nut that sits underneath the center screw moves the lamp's position horizontally and vertically. Loosening this nut will free the lamp assembly from the cap housing. The user can then push the entire adjustment screw and lamp along the plane to center the lamp in the reflector, evening the beam.


Lamps


HPL incandescent

The proprietary HPL (High Performance Lamp)
lamp Lamp, Lamps or LAMP may refer to: Lighting * Oil lamp, using an oil-based fuel source * Kerosene lamp, using kerosene as a fuel * Electric lamp, or light bulb, a replaceable component that produces light from electricity * Light fixture, or ligh ...
uses a compact filament, which concentrates the most light where it is efficient in an ellipsoidal reflector. At 575
watt The watt (symbol: W) is the unit of power or radiant flux in the International System of Units (SI), equal to 1 joule per second or 1 kg⋅m2⋅s−3. It is used to quantify the rate of energy transfer. The watt is named after James Wa ...
s, HPL lamps can produce as much light as an older 1000 watt lamp. Source Four is named for the HPL, its light source, having four filaments. It is also available in 375 W and 750 W versions, at a variety of rated supply voltages. HPL lamps are also available in longer-life versions that reduce the
color temperature Color temperature is the color of light emitted by an idealized opaque, non-reflective body at a particular temperature measured in kelvins. The color temperature scale is used to categorize the color of light emitted by other light sources ...
from 3250 K to 3050 K to give the lamp a life of around 1500–2000 hours as opposed to the 300-400 hour life of the standard HPL.


Other versions

ETC also manufactures a high-intensity discharge (HID) Source Four body with a
metal-halide lamp A metal-halide lamp is an electrical lamp that produces light by an electric arc through a gaseous mixture of vaporized mercury and metal halides (compounds of metals with bromine or iodine). It is a type of high-intensity discharge (HID) ga ...
. The fixture has a small box attached to the yoke of the fixture which contains the ballast and other additional control gear required to strike and operate an HID lamp. HID lamps are not dimmable. The HID fixture uses less energy than the standard HPL lamp. A range of Source Four instruments using
LED A light-emitting diode (LED) is a semiconductor Electronics, device that Light#Light sources, emits light when Electric current, current flows through it. Electrons in the semiconductor recombine with electron holes, releasing energy i ...
s are also available. The shutter, barrel, and lens tubes are identical to the HID and tungsten versions of the Source Four. Control of parameters such as color and light intensity is available via DMX. The power usage is approximately 25% of that of the equivalent tungsten version, although the purchase cost is significantly higher. Lamp life is significantly higher, retaining 70% of its original intensity at 50,000 hours.


Barrel

The Source Four is the first fixture to feature a rotating shutter barrel, 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 made from
stainless steel Stainless steel is an alloy of iron that is resistant to rusting and corrosion. It contains at least 11% chromium and may contain elements such as carbon, other nonmetals and metals to obtain other desired properties. Stainless steel's corros ...
, which does not warp as easily under the heat of the lamp. The shutters are arranged in 3 planes, allowing a degree of freedom in shutter placement by the extreme angles they can be racked to. The top and bottom shutters are on their own plane, with the 2 side shutters sharing a single plane. 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. According to ETC's manual, the lenses in each lens tube cannot be reoriented, added or removed. 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. The exception to this is the Source Four Zoom. The Source Four Zoom has a longer barrel, and it has a lens which changes the focal point by moving forward or backward. Different field angles are needed for different venues with different
catwalk A fashion show ( French ''défilé de mode'') is an event put on by a fashion designer to showcase their upcoming line of clothing and/or accessories during a fashion week. Fashion shows debut every season, particularly the Spring/Summer and Fa ...
and electric systems (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 Scrim can refer to: * Scrim (material), either of two types of material (a lightweight, translucent fabric or a coarse, heavy material) * Scrim (lighting), a device used in lighting for films * Scrim (internet slang), friendly match between tea ...
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 A technician is a worker in a field of technology who is proficient in the relevant skill and technique, with a relatively practical understanding of the theoretical principles. Specialisation The term technician covers many different speciali ...
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 changing the lens tube. This is needed 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 released 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 barrels. 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

Although the Source Four is designed to accept the same types of accessories as other lighting instruments, when launched in 1992 the smaller lens and barrel size required accessories that fit in a 6.25" holder rather than the 7.5" that was the standard for Lekos at the time. Many third-party manufacturers have designed products specifically for the Source Four. Ocean Thin Films, a manufacturer of scientific optics and instruments, offers the
SeaChanger Color Engine The SeaChanger Color Engine is an electro-mechanical device that is used to control light color in entertainment-industry lighting applications. The unit employs four overlapped color filter wheels, inserted into a light beam near its source, to ...
that utilizes gradient dichroic disks to control color. The unit is mounted in between the lamp assembly and optics and is controlled via
DMX512 DMX512 is a standard for digital communication networks that are commonly used to control lighting and effects. It was originally intended as a standardized method for controlling stage lighting dimmers, which, prior to DMX512, had employed ...
. Great American Market (GAM) offers a special effects unit, the SX4, that is mounted inside a Source Four in a similar manner to the Seachanger Color Engine and offers a large selection of drop-in accessories that range from gobo-changers to overlapping looping gobos. Several manufacturers of HMI sources, such as Kobold, provide lighting fixtures that provide "daylight balanced" light through the Source 4 without the use of
gels A gel is a semi-solid that can have properties ranging from soft and weak to hard and tough. Gels are defined as a substantially dilute cross-linked system, which exhibits no flow when in the steady-state, although the liquid phase may still di ...
. This is accomplished by replacing the lamp assembly on the back of the Source 4 with an HMI lamp head.


Other Source Four products

In 1995, ETC introduced the
Source Four PAR The Source Four PAR is a stage lighting instrument manufactured by Electronic Theatre Controls. The name of the fixture derives from the stylistic and construction features it shares with ETC's Source Four. The suffix identifies the Source Four ...
which is meant to replace traditional PAR cans. It uses the HPL lamp, and has interchangeable lenses. In 1999, ETC introduced the Source Four PARNel as an alternative to
Fresnel lantern A Fresnel lantern (pronounced ''frəˈnɛl or fruh-nel'') is a common lantern used in theatre that employs a Fresnel lens to wash light over an area of the stage. The lens produces a wider, soft-edged beam of light, which is commonly used for bac ...
s. In 2002, ETC introduced the Source Four MultiPAR as an alternative to striplights. In 2004, ETC introduced the
Source Four Revolution Source may refer to: Research * Historical document * Historical source * Source (intelligence) or sub source, typically a confidential provider of non open-source intelligence * Source (journalism), a person, publication, publishing institute o ...
, ETC's first moving fixture. The Revolution was awarded both the EDDY and ABTT awards. The Revolution has the same filament structure as famous HPL Source Four lamp, as opposed to most other moving lights, which use arc lamps, or, more recently, LEDs. Also, the Revolution uses a gel string color scroller instead of the typical color wheel, thus allowing lighting designers to use familiar gel choices. In 2011, ETC introduced the
Source Four Fresnel Source may refer to: Research * Historical document * Historical source * Source (intelligence) or sub source, typically a confidential provider of non open-source intelligence * Source (journalism), a person, publication, publishing institute o ...
, which is a
fresnel Augustin-Jean Fresnel (10 May 1788 – 14 July 1827) was a French civil engineer and physicist whose research in optics led to the almost unanimous acceptance of the wave theory of light, excluding any remnant of Newton's corpuscular theo ...
light that uses the HPL lamp.


References

{{reflist Stage lighting instruments