Cinematography-Theory-And-Practice

Figure 10.27. (top) A Sekonic Dual-Master light meter. It is a combinationof both an incident meter and aspot meter. It can read both continuouslight and strobes.Figure 10.28. (bottom) A closeup ofthe readout for the Sekonic meter.In the upper right is the ISO (320 inthis case). On the left is the framerate — 24 frames per second (24 f/s).Middle right is the reading: f/4. Thesmaller numbers are 1/10 of a stop,in this case 2/10th, which you wouldprobably round off to 1/3 of stop, fora lens setting of f/ 4 and 1/3rd.At the bottom is a graphic indicatorof the f/stop. This meter can takeseveral readings and average them ifyou wish.Figure 10.29. (below) A reflectanceor spot meter by Pentax. This one hasa Zone scale added to the barrel.The classical practice, however, is to point the hemisphere directlyat the lens and eliminate only the backlights, then take a readingexactly at the subject position. Reading key, fill, and backlight separatelyis in fact only a way of determining the ratios and looking forout-of-balance sources. In most instances, reading the key light iswhat determines the exposure — how the lens aperture will be set.Later we will look at applications that go beyond the simple classicalapproach and are useful in dealing with unusual situations. Mostmeters that are used with the diffusing dome also come with a flatdiffusing plate that has a much smaller acceptance angle (about 45°to 55°). This means that the angle of the light falling on the platehas an effect on the reading, just as it does in illuminating a subject.The flat plate makes taking readings for individual lights simplerand is also useful for measuring illumination on flat surfaces, such asin art copy work. Incident meters are generally also supplied with alenticular glass plate that converts them to wide acceptance reflectancemeters. These see little use on most sets as they have very wideFor the most part, incident meters are set for the film speed andshutter speed being used (either electronically or by using slide-inplates) and then read out directly in f/numbers.The Reflectance MeterReflectance meters, (most frequently called spot meters) read the luminanceof the subject, which is itself an integration of two factors: thelight level falling on the scene and the reflectivity of the subject. It is whyOn the face of it, this would seem to be the most logical method ofreading the scene, but there is a catch. Simply put, a spot meter willtell us how much light a subject is reflecting, but this leaves one verybig unanswered question: how much light do you want it to reflect?In other words, incident meters provide absolute readouts (f/stops),while spot meters provide relative readouts that require interpretation.While many spot meters were formerly calibrated in exposurevalue (EV) units, most provide direct readout in f/stops, which canbe a source of confusion.Think of it this way: you are using such a meter and photographinga very fair-skinned girl holding a box of detergent in front of asunset. You read the girl’s face: f/5.6, the box reads f/4, the sky isf/22. So where are you? Not only do we not know where to set theaperture, we don’t even know if the situation is good or bad. Let’sstep back a moment and think about what it is that light meters aretelling us. To do this we have to understand the cycle of tone reproductionand lay down a basic system of thinking about it.THE ZONE SYSTEMWe must remember that the exposure values of a scene are not representedby one simple number: most scenes contain a wide range oflight values and reflectances. In evaluating exposure we must lookat a subject in terms of its light and dark values: the subject rangeof brightness. For simplicity we will ignore its color values for themoment and analyze the subject in terms of monochromatic values.Let’s visualize a continuous scale of gray values from completelyblack to completely white (Figure 10.39). Each point on the grayscale represents a certain value that is equivalent to a tonal valuein the scene. In everyday language we have only vague adjectiveswith which to describe the tones: “very dark gray,” “medium gray,”cinematography200