Abstract: Apparatus for modifying a beam of light, comprising at least one set of blades moveable across the beam, wherein each set of blades is arranged into a first subset of blades and a second subset of blades, and wherein the respective subsets of blades are axially spaced from each other. The apparatus is particularly suitable in apparatus comprising a light source and means for directing and/or focusing the light, and may be embodied (a) in a color changer for changing the color of light in a light beam, (b) in a diaphragm for varying the aperture, and (c) in dimmer apparatus for dimming light beam.