The ETC Source Four is a precision-engineered ellipsoidal lighting fixture widely used in theatrical and stage environments for its high-quality optics and efficient light output. It utilizes a patented HPL lamp combined with a faceted dichroic reflector to deliver a bright, even beam while minimizing infrared heat, which helps extend the life of gels and accessories. The fixture supports interchangeable lens tubes with field angles ranging from 5° to 90°, and includes a rotating barrel and stainless-steel shutter assembly for detailed beam shaping. Its rugged die-cast aluminum housing and tool-free lamp adjustment make it suitable for demanding production settings. The Source Four is compatible with a variety of accessories, including gobo holders and iris units, and is known for its crisp pattern projection and consistent performance across a range of lighting applications.