An illumination system (10), comprising an illumination source (2) and a mechanical dimming device (4) for dimming the amount of light generated by the illumination source (2) and emanating from the lighting apparatus, comprising an array of partially overlapping blades, the array of blades being mechanically operable to define an optical passageway there through of variable cross sectional area, wherein each blade comprises at least one overlapping segment and at least one non-overlapping segment, the overlapping segments being a color filter and the non-overlapping segments being a shutter. In a preferred embodiment the color of the color filter is in the range from yellow to amber to red. This arrangement is especially useful with a high intensity lamp as the illumination source, and provides for natural dimming of the light produced by the illumination source over the range of from about 0 to 100% causing a color change in the projected light that resemble natural sunset.