Cinematography-Theory-And-Practice

THE TOOLS OF LIGHTINGCinematographers do not need to know all the details of how eachpiece of lighting equipment works, but it is essential that they knowthe capabilities and possibilities of each unit, as well as its limitations.A great deal of time can be wasted by using a light or piece of gripequipment that is inappropriate for the job. One of the DPs mostimportant functions is ordering the right lighting equipment for thejob and using it appropriately. Motion picture lights fall into sevengeneral categories: HMIs, tungsten Fresnels, tungsten open face lights,fluorescents, xenons, practicals, LED lights, and sunguns.Figure 8.2. (above) A 12K HMIFresnel.Figure 8.1. (previous page) AnAirstar balloon light used for alarge night exterior.DAYLIGHT SOURCESLighting units can generally be divided into those that output daylightbalance or tungsten balance light. Several types of light are daylightbalance: HMIs and color correct fluorescents and LED units among them.Color Rendering IndexLights are classified according to Color Rendering Index (CRI), whichis a measure of the ability of a light source to reproduce the colors ofvarious objects faithfully in comparison with a natural light source.This means that a light with a low CRI will not render colors accurately.A CRI of 90 or above (on a scale of 0 to 100) is considerednecessary for film and video work (and also still photography). TheCRI is especially important when judging fluorescent and other gasdischarge sources. For most HMIs and color-correct fluorescents,LEDs, and other units designed for film work, the color renderingindex is greater than 90.HMI UnitsHMIs generate three to four times the light of tungsten halogen,but consume up to 75% less energy for the same output. When atungsten bulb is color-corrected to match daylight, the advantageincreases to seven times because a great deal of the spectrum isabsorbed by the blue gel (color temperature blue or CTB). See thechapter Color). Because HMIs (Figure 8.2) are more efficient in convertingpower to light, they generate less heat than a tungsten lampwith the same output.HMI stands for the basic components: H is from the Latin symbolfor mercury (Hg), which is used primarily to create the lamp voltage.M is for medium-arc. I stands for iodine and bromine, which arehalogen compounds. The halogen serves much the same function asin a tungsten halogen lamp in prolonging the useful life of the bulband ensures that the rare earth metals remain concentrated in the hotzone of the arc.HMI lamps have two electrodes made from tungsten, which projectinto a discharge chamber. Unlike tungsten bulbs, which have acontinuous filament of tungsten wire, HMIs create an electrical arcthat jumps from one electrode to another and generate light and heatin the process. Color temperature (see the chapter Color) as it is measuredfor tungsten bulbs or sunlight does not technically apply toHMIs (or to other types of discharge lighting such as fluorescents)because they produce a quasi-continuous spectrum. In actual practice,though, the same measurements and color temperature metersare used for all types of video and motion picture lighting sources.Our eyes are unreliable in judging color because our brain adjustsand compensates; it will tell us that a wide variety of colors are“white.” A color meter or vectorscope is a far more dependable ways ofjudging color; however, they do not measure CRI.cinematography130