From the AACT Knowledge Base Aligning Ellipsoidals Do it periodically. Here’s how.

The great advantage of the ellipsoidal spotlight is that the beam edge can be varied from a sharp to a soft focus, providing great precision in directing light. However, because the lamp and reflector are separate parts of the instrument, ellipsoidals must be realigned periodically to make sure the lamp filament is centered on or near the focal point of the reflector. Otherwise they will not provide optimum light output. While many lighting people simply aim the instrument at the stage floor, the best method is to aim at a matte surface (preferably white or pale gray) about ten feet away, says lighting expert Glen Cunningham, author of Stage Lighting Revealed. Most ellipsoidals have three screws on the cap of the instrument which you turn until you have the brightest, most even field. (A fourth screw, located equidistant between the three adjustment screws, is used to lock the position of the socket plate and must be loosened to make the adjustments.) Experiment with the screw adjustments, since each lamp is a little different. First, adjust the barrel for the hardest edge possible. Loosen the center screw to allow adjustment of the others, Cunningham advises, "then adjust the screws to get the hot spot in the center of the beam. Then decide what kind of alignment you want. The three most popular settings are flat, cosine, and peak, and each gives a slightly different beam. "For a flat setting, adjust the lamp for the most even beam while keeping everything centered. For a cosine setting, adjust the lamp so that your center is a little hotter and the area two-thirds from the beam center is 50 percent as bright as the center (a light meter helps, but you can eyeball it). For peak, just get the hottest spot you can in the beam's center." Some ellipsoidals use a small "joystick" to adjust the lamp position and achieve the best field, but like many other lighting people, Cunningham prefers the screw method. "I have worked in theaters that had both types of instruments," he recalls. "The screw style needed only periodic adjustment. But the joystick style were almost always out of alignment because people just can't keep their hands off the things. They're constantly moving the joystick around 'to get the best alignment.' Meanwhile the hangs take longer and the instruments are never aligned well because a hang isn't the best time, place, or setup for the job. "I've also found that most joysticks just move the lamp from side to side. They give 360- degree adjustment on a single plane, while the screws give you the ability to pivot the lamp around its axis. With all the joysticks I've used, the adjustment was limited by the diameter of the hole in the reflector and the diameter of the lamp bulb." Another problem with joystick-style instruments is that, in many cases, to get to the lamp you must first loosen and remove the depth adjustment. This is a problem when you need to make a fast change, such as during performance, where you can't turn on the instrument to ensure proper realignment.

[A version of this story first appeared in Stage Directions magazine.]

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