Light—Science & Magic- P4

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Light—Science & Magic- P4 LIGHT—SCIENCE & MAGIC 6.26 The same scene as in Figure 6.24, but with a lens polarizer removing reflection from the glass. The polarizer does not affect the metal. no light. Together, these facts suggest that the front of the metal cannot be lit. However, we have also said that the black plastic is glossy. And we know that glossy things do produce direct reflection, even if they are too black to produce diffuse reflection. This means that we can light the metal by bouncing light off the plastic surface as in Figure 6.27. If you examine the angles, you see that a light under the camera can bounce light from the glossy plastic to the metal. That light strikes the metal at such an angle that it then reflects back to the camera to record on film. The metal is lit, and the bright metal in Figure 6.28 proves it. As far as the metal can tell, it is being lit by the plastic surface in the scene. However, the camera cannot see that light is reflecting from the black plastic; the family of angles defined by the plastic makes it impossible. Like the earlier glass surface, the acrylic surface will reflect the overhead light source. Once again, we used a polarizing fil- ter on the lens to eliminate the glare. Finally, notice that the front of the box now shows a texture not seen in the earlier examples. This is because invisible light is only effective in a small area on the tabletop. When metal is not absolutely flat, the family of angles required to light it 138 METAL 6.27 “Invisible” light reflected from the glossy black plastic lights the metal. No light reflects directly from the plastic to the camera, so the camera cannot see the light source for the metal. Glossy Black Acrylic 6.28 The result of “invisible” light. The light source for the box is in the scene—the black plastic directly in front of it. 139 LIGHT—SCIENCE & MAGIC becomes larger. Next we’ll examine an extreme example of that circumstance. ROUND METAL Lighting a round piece of metal begins, like any other metal shape, with an analysis of the family of angles that produces direct reflection. Unlike any other metal shape, the family of angles defined by a piece of round metal includes practically the whole world! Figure 6.29 shows the relevant family of angles for a camera photographing a round metal object at a typical view- ing distance. Remember, lighting metal requires the prepara- tion of a suitable environment. Round metal requires a lot more work to light because it reflects so much more of that environment. Notice that the camera will always be in that environment seen by the metal. There are no view-camera tricks to remove the camera from the family of angles reflected by round metal. Furthermore, the reflection of the camera will always fall exactly in the center of the metal subject, where it is most noticeable to the viewer. For this exercise we will use the most difficult example possi- ble: a perfectly smooth sphere. Figure 6.30 shows the problem. ily of Angles Fam 6.29 The family of angles for a round metal subject includes the Round Metal whole environment, including the camera. 140 METAL 6.30 The common problem presented by round metal. The first step in fixing this problem would be to get rid of unnecessary objects. However, the camera is the one offend- ing object that no cleanup effort can remove. There are three ways to eliminate the camera reflection: we can camouflage the reflection, keep the camera in the dark, or put the subject in a tent. Camouflage For our purposes, camouflage is any desirable clutter that helps make unw ...