Built-in Dimmers are oh-so-convenient. If a cloud screws up the relation of an artificial fill or you just want less heat on the side of her face, bliss is just a twist away. But how useful are these built-in dimmers in creating dramatic changes in exposure? Are the dimmers really calibrated to be useful to a precise cinematographer? I tested three popular lights to compare which lights had the most useful dimmer system: the 1×1 Lightpanel (LED), the Kinoflo Diva (daylight fluorescent), and the Bron Kobold 400 Watt All-Weather System (HMI). The criterion for a “useful dimmer” included a consistent fall-off rate in exposure (f-stop) as the light is dimmed (proportionally) and accurate visual measurement markings around the knob corresponding to the change in brightness measured. If I’ve turned the knob halfway but the light hasn’t cut down at all, I’m not happy.
And just so that this blog post isn’t too technical or stuffy, we won’t do any math or go over the scientific proceedings. Just know it involved me, a light meter, some blocking tape, and a garage with no outside light. And we’ll refer to my crudely drawn and scanned-in graph (below) to draw some lofty conclusions.
If you glance briefly at the graphs (but don’t scrutinize them too much) you’ll see the LED easily wins for best dimmer system. Its results form the closest semblance of a linear graph. Even more surprisingly, I found that the incremental knob markings accurately cut the light between a ½ or full stop all the way to the 25 mark. Second place goes to the Kinoflo Diva. It got off to a rocky start, but eventually started dimming noticeably. However, I quickly realized that the dimmer markings were more of a nice yellow design and not meant to be accurate in the least. The arbitrariness of the Kinoflo Diva, regardless of marked change near the end, make it useful for quick, sizable adjustments, but it is not nearly as precise and nuanced as the LED. Furthermore, it can turn from 4 bulbs to 2 bulbs, which probably mirrors its dimmer in its restrictedness. So what’s the point of the dimmer? The HMI finished last—and who could blame him? HMIs already rock and have nothing to prove (this one is even waterproof) but if it’s not going to dim in any noticeable way, don’t waste our time with a dimmer system. Perhaps this is due to a poorly executed experiment (I’m a film major, take it easy), or maybe the HMI takes longer to warm up to its dimmer settings. But those last minute touches can’t freeze a shoot for five minutes as the HMI gets its act together. Clearly, then, the HMI has arbitrary markings on its ballast and isn’t too concerned with dimming itself. But it is still the brightest. We’ll give it a point for that. Here’s the data if you really really really like dimming/mood lighting/being picky about exposure/like turning knobs. KINOFLO Diva (fluorescent) Full = f/8 2 clicks dimmed= f/8 4 clicks dimmed = f/8 6 clicks dimmed= f/8 7 clicks dimmed= f/5.6 8 clicks dimmed= f /2.8-4 split 9 clicks dimmed = f/2 all the way down (but not off)= f/1.4 Bron Kobold 400 Watt All-Weather System (HMI) Full= f/8-11 split 1 click= f/8 and ¼ 2 clicks= f/8 3 clicks= f/8 4 clicks= ¼ under f/8 5 clicks = f/5.6-8 split 6 clicks = f/5.6-8 split off= underexposed. 1×1 Lightpanel (LED) 100%= f/8 90%= f/ 5.6-8 split 80%= ¼ under f/5.6 75%= f/4 65%= f/2.8-4 split 50%= f/2-2.8 split 35% = f/2 25%= underexposed 15%= underexposed off= underexposed -Bryan Sih, Fall 2013 Intern, Boston University
