ERS (Ellipsoidal Reflector Spotlights) are also sometimes known by their brand names, especially Leko, short for Lekolite, the name given to them by their inventors, Joseph Levy and Edward Kook. ETC’s Source Four has become a very popular ERS throughout the industry, and some people use the term Source Four to refer spotlights in general. They come in many forms, and are the most numerous and important instrument type in use. The flexibility of the ERS allows them to fulfill the bulk of the lighting roles in the theatre, from area lighting to close specials, from long throws from the back of the house to shin kickers on the stage.
ERS’s may have more than one focusing lens, while all possess internal shutters for cropping the emitted light, and all accept a color gel in front of the lens and a gobo in front of the shutters. ERS’s may have bulbs mounted axially, or with the base either up or down (it is important to hang a lamp in the proper orientation). The lenses are smooth and full, not stepped, and it is the lens or lenses that move in the ERS, not the bulb and reflector assembly as in the Fresnel.
The ERS improves over the efficiency of the Fresnel by surrounding the bulb in an ellipsoidal reflector, with the filament of the bulb at one focus and the aperture to the lens housing at the other. The shutters and gobo are ideally in focal point of this aperture. (In UK: the term ERS is not often used. An ERS is simply considered a very good profile.)
This is a 6″ Fresnel. The Fresnel uses a Fresnel lens, hence, its name. This unit provides a soft, circular light and is often used for back light and down light. At least in our theater.
Fresnels are typically 8-, 6- or 4-inch, referring to the diameter of the lens. The lens is the distinctive ‘Fresnel lens’ type, with a ‘stepped’ appearance instead of the ‘full’ or ‘smooth’ appearance of other lenses. The stepped nature of the lens causes a corresponding pattern of circles of light, so Fresnel lenses are usually ‘stippled’ on the flat side. This pattern of small bumps helps to break up the light passing into the lens to smooth out its eventual pattern.
Fresnels use a spherical reflector, with the filament of the bulb at the focus. Due to this, the bulb and reflector cannot move independently of one another, and remain a fixed unit inside the housing. It is this unit that is moved back and forth inside the lamp to focus the fresnel. This is done by a slider on the bottom of the light, or by a worm track.
Fresnels are not very efficient. The reflector cannot be larger than the lens aperture, and thus all the radiated light that is neither reflected by the parabola behind the bulb or emitted directly through the lens is absorbed by the casing as waste heat. Additionally, the degree to which the lamp may be focused is limited by the length of the housing. The tighter the focus (‘spotted in’) the less light is able to escape. Thus fresnels are not good for tight focus on small areas. Fresnels also lack internal shutters, and must rely on barndoors, large metal flaps that may be mounted just beyond the color slot at the front of the light. Due to these restrictions, Fresnel are most often used at middling distances for area lighting.
Fresnel bulbs are almost always ‘base down’: mounted with the bulb up. Burning these lamps upside down will shorten lamp life significantly. (In UK: Fresnels are not spotlights, they are Fresnels.) Your content goes here. Edit or remove this text inline or in the module Content settings. You can also style every aspect of this content in the module Design settings and even apply custom CSS to this text in the module Advanced settings.
This is a 1000Q Follow Spot. Altman. One word of caution. Please have at least two people to raise or lower this light on it’s stand. I’ve seen, too often, somebody trying to lower it and get their hand caught and pinched.
Some of our units are Altman 360 units. (left) The difference being that they lack the Q. So?? The Q stands for Quartz which is the type of Lamp used. The Non-Q units use an Incandescent Lamp. You can tell the difference just by looking at the unit. The lamp housing of the Q unit (right) is straight up on the top. The incandescent unit’s lamp housing is shaped like a Banana, off to one side.