The Family Of Anglesfamily of angles that produces direct reflection. In theory, we could also talk about the family of angles that produces diffuse reflection. However, such an idea would be meaningless because diffuse reflection can come from a light source at any angle. Therefore, when we use the phrase family of angles, we will always mean those angles that produce direct reflection.
This family of angles is important to photographers because it determines where we should place our lights. We know that light rays will always reflect from a polished surface, such as metal or glass, at the same angle as that at which they strike it. So we can easily determine where the family of angles is located, relative to the camera and the light source. This allows us to control if and where any direct reflection will appear in our picture. Figure 7 shows the effect of lights located both inside and outside this family of angles. As you can see from Figure 7, any light positioned within the family of angles will produce a direct reflection.
outside of the family of angles will not light a mirror-like subject at all, at least as far as the camera can see.
Photographers sometimes want to see direct reflection from most of the surface of a mirror-like subject. This requires that they use, or find in nature, a light large enough to fill the family of angles. In other scenes, they do not want to see any direct reflection at all on the subject. In those instances, they must place both the camera and the light so that the light source is not located within the family of angles.
Applying The TheoryExcellent recording of a subject requires more than focusing the camera properly and exposing the picture accurately. The subject and the light have a relationship with each other. In a good photograph, the light is appropriate to the subject and the subject is appropriate to the light. The meaning of appropriate is the creative decision of the photographer. Any decision the photographer makes is likely to be appropriate if it is guided by understanding and awareness of how the subject and the light together produce an image.
Light: Science & Magic by Fil Hunter, Steven Biver and Paul Fuqua is available at Amazon and other retailers.
Photographers diffuse the light source, whether it’s a strobe or a continuous source by reflecting the light from an umbrella or by covering it with a translucent material. We call light passing through translucent material diffuse transmission. Now we speak of diffuse reflection. The two concepts have enough in common that we should pay special attention to the differences between them.
Diffusing the light source has no effect on whether the reflection is diffuse. Remember that small light sources are always “hard” (undiffused) and that large light sources are almost always “soft” (diffused). Strobes, for instance, are a classic hard source until you modify them with a softbox or other modifier.
Then notice that our figures show diffuse reflections produced by both diffused and undiffused light sources. Similarly, you can see direct reflections produced by diffused and undiffused light sources.
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