ETC S4 Profile Iris is a mechanical iris insert for S4 Profile luminaires that provides adjustable beam control. The module installs within the fixture's iris slot and is actuated by a front-access knob, delivering a variable aperture from wide to narrow without altering color temperature. The iris uses a blade-based aperture with a restrained linkage for repeatable positioning, preserving focus and edge sharpness while reducing stray light. No external power is required.