An ETC Source Four Lens Tube – 90º is an ultra‑wide lens designed for extremely short throw distances where maximum coverage is needed. The 90º beam spreads light across a very large area, making it useful for close‑mounted fixtures that need to cover wide sections of a stage or performance space from nearby positions. This lens is often used for front light, fill light, or special applications where fixtures are placed close to the subject and narrower lenses would create hot spots or uneven coverage. It installs directly into compatible Source Four ellipsoidal fixtures and is typically chosen when wide, even illumination is the priority.