Ellipsoidal

Overview

An Ellipsoidal – fully Ellipsoidal Reflector Spotlight (ERS), also known in German-speaking countries as a profile spotlight and colloquially often called a "Leko" – is a type of luminaire that produces a sharply defined, precisely shapeable beam of light. Characteristic is the combination of an ellipsoidal reflector that focuses the lamp's light and a downstream lens system that projects the beam. The optics function similarly to a slide projector: the lamp sits at one focal point of the reflector, and the gate with the beam shapers at the other.

"Leko" (from Lekolite) and "Source Four" are originally brand names that are often used generically for any type of ellipsoidal. In contrast to a Fresnel or PC spotlight, which provides a soft, diffuse beam, the ellipsoidal is designed for a hard, controllable edge and for projecting patterns.

Construction and Function

Beam shaping is the core feature of the ellipsoidal:

• Shutters: Typically four metal blades at the internal focal point, used to trim the beam of light to straight edges – for example, to keep light precisely off a wall.
• Gobo Slot: A holder in the gate for metal or glass gobos, used to project patterns and textures (e.g., window, venetian blind, or foliage shadows).
• Iris: Many models have an iris diaphragm to continuously reduce the size of the circular beam.
• Lens Tube: Interchangeable or sliding lens tubes (often one or two plano-convex lenses) determine the beam angle and allow focusing between a soft and hard (in focus) edge.

Technical Data

Ellipsoidals are classified by their field or beam angle; interchangeable lens tubes typically cover a range from approximately 5° (very narrow) to 90° (very wide). Older units were designated by lens diameter and focal length (e.g., 6x9). Traditionally, tungsten-halogen lamps were used as the light source; increasingly, LED versions are available.

A common reference fixture is the ETC Source Four: it uses an HPL halogen lamp (according to the manufacturer in power ratings of 375 W, 575 W, and 750 W) and a dichroic "Cold Mirror" reflector that filters out a large portion of the infrared heat from the beam.

Set Usage

On a film set, the ellipsoidal is used when light needs to be precisely placed and cut: for targeted "sun hits" through windows, for sharply defined areas of light (e.g., a light path under a door), or for projected shadow patterns using gobos. The shutters allow the beam to be precisely limited to an area without casting spill light onto adjacent surfaces. Tungsten versions provide a warm, artificial light typical color temperature; LED models offer adjustable color temperature and colors depending on the design.