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|Category:||Studio Lighting and Flash|
Direct Vs Diffuse Light Reflection - Tips on bouncing light off different types of surfaces.
|This tutorial is an extraction from page 45 of the Speedliter's Handbook by Syl Arena. You can find more information about this title on the Pearson website.
It's easy to understand how light bounces off a reflective surface like a mirror. What about a matte surface, like a piece of paper? Does the angle of reflection still equal the angle of incidence? More specifically, why are you not blinded when reading a newspaper outdoors in full sun?
The answer lies in the surface of the paper. If you look at it microscopically, you would see that it is rough. The light is still reflecting off at an angle equal to the angle of incidence. It’s just that the text of the paper gives it surfaces that face many directions.
The shots (bottom) provide a good example of the difference between direct reflection and diffuse reflection. Figure 3.9 was lit directly by an incandescent bulb in a silver reflector. Infact, you can see it reflecting in the surface of the olive oil. The liquid surface of the oil and the metallic surfaces of the knife and plate all create direct reflections. Figure 3.10 is the exact same shot with the addition of a Lastolite Skylite panel between the light and the plate (as shown in Figure 3.11). I’m sure you’ve noted that the glare on the olive oil, silver knife and gold plate is no longer a problem. The 42" diffusion panel replaced the 6" reflector as the light source—sending light from multiple angles rather than just one.
Just as important, did you also notice in the upper corners of the photos that the brightness of the tablecloth did not change? It remains the same tone of medium-gray. This is because the textured surface of the fabric provides a diffuse reflection—even when lit directly.
|Figure 3.9 - Direct reflection creates glare in the surface of the liquid and metallic surfaces.||Figure 3.10 By inserting a diffusion panel in front of the light, the direct reflection has been tamed. Notice also in both shots that the tone of the tablecloth remains the same. Even when lit directly, the fabric provided a diffuse reflection.|
Figure 3.11 The placement of the 42" Lastolite Skylite panel with diffusion fabric.
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