Cinematography-Theory-And-Practice

Zones in a SceneExamine a typical scene with the spot meter — see Figure 10.32. Ifyou assign the darkest value to Zone 0 you can then find areas thatestarea: these are Zones I through X. This is an important exerciseand is vital to understanding exposure control. Ignoring the effect ofthe scene through a viewing glass, which is a neutral density filter.Now picture each of these tonal values arranged in ascending order.What you have is a grayscale, and fortunately it is a commonly availableitem. Most grayscales are made to reasonable rigorous densitometricstandards and are useful calibration tools. Let’s take a look atwhat it really is (Figure 10.31).THE GRAY SCALEThere are a great many grayscales but, they all have one thing incommon: they vary from black to white. Most are divided into sixto ten steps, but they certainly don’t have to be: some are 20 steps ormore. How white the white is and how black the black is vary somewhatdepending on the printing quality and the materials involved.Some scales include a piece of black velvet, since black paper cannever be truly black. For our purposes, we will consider only grayscaleswhere each step represents one full “stop” increment over theprevious, — where each step is √2 times the reflectance of the previousone (Table 10.4).Why 18%?foreassume it to be 50% reflectance. It isn’t — it is 18% reflectance.The reason for this is that the eye perceives changes in tone logarithmicallyrather than arithmetically, as we saw above. If each zonewere, for example, 10% more reflective than the previous, the eyewould not read it as a smooth spectrum.Discussion of the zone system is always in terms of grays, but anycolor can be interpreted in terms of its gray-scale value. The importanceof value cannot be stressed too much. The value relationshipsbetween colors carry about 90% of the information in any picture.In a black-and-white photograph the gradients of light and shadowon surfaces contains the information about form, clearly defining allthe objects. Color contributes a relatively small amount of actualpicture information, but a great deal of the beauty and interest ofthe picture.ZONE DENSITY DESCRIPTION0 0.02 Pure black - Dmax.I 0.11 1st perceptible value lighter than black.II 0.21 Very, very dark gray.III 0.34 Fully textured dark gray.IV 0.48 Dark middle gray.V 0.62 Middle gray - 18% reflectance.VI 0.76 Light middle gray.VII 0.97 Fully textured light gray.VIII 1.18 Very light gray.IX 1.33 First perceptible gray darker than pure white.X 1.44 Pure white - Dmin.Zone X 100%Zone IX 70%Zone VIII 50%Zone VII 35%Zone V 18%Zone IV 12%Zone III 9%Zone II 6%Zone I 4.5%Zone 0 3.5%Table 10.4. Percentage of reflectancefor Zones. These are reflectancevalues of the subject.Table 10.5. Zones, negative densityand description.exposure203