Ever spent a few minutes balancing atop a case, fiddling with focus, clipping diffusion gels to barndoors and feathering a fresnel that's 8 feet in the air in order to fine tune a backlight? If so, then you already know that nothing is sweeter than dialing in just the right amount of light in mere seconds with a dimmer.
Don't have one? You should. You can build your own in fewer than 30 minutes for under $30 with a handful of components available at any hardware or home improvement store. Your shopping list should include a single-gang switch box with 1/2-inch knockouts, a pair of 1/2-inch cable clamps, an electronic dimmer (600 W minimum) with a sliding control lever, a trim plate with a rectangular opening to fit the dimmer, four wire nuts, and a 14- or 16-gauge 6-foot extension cord with three-pin plugs molded on.
Assemble your portable dimmer by removing knockouts and fitting the cable clamps into opposite ends of the box. Cut the extension cord in half, strip back 3 inches of outer jacket on both sides of the cut and then strip 3/8-inch of insulation from the end of each wire. Thread one piece of the severed and stripped cord through each cable clamp, strip the three wires attached to the dimmer and, using wire nuts, make four splices: Connect all three green wires together (both whites); then connect one of the black wires on the dimmer to either of the blacks from the cords and then splice the remaining two black wires. Twist the wire nuts so they're really tight and review the connections: three greens, two whites, black-black and black-black.
Assemble by centering the cords so an inch of the outer jacket remains in the box, positioning the wire nuts so they lay side by side on the bottom, and then ease the dimmer into the box until it is flush with the top. Secure the dimmer using the supplied screws. Now gently tighten each cable clamp to grip the cord without crushing it and finish the job by attaching the trim plate. You may need to shorten the trim plate screws if they bottom out before the plate is secure.
That's it. Test it and then toss it in your kit. And every time you use it you'll ask yourself, "Why didn't I do this a long time ago?"
