Wednesday, February 13, 2013

Hiding in the shadow

On February 8th at his Public Speakers Blog Steve Siebold posted a four-minute video about The Single Most Important Speaking Secret, which he said is energy. I agree, but when I saw it, I just burst out laughing and shouted: “Aziz, light!”

While the background is bright and clear, his face sometimes goes into shadows and looks murky. That unintended visual style is like film noir. What went wrong, and how could it be fixed?

The exposure meter on a still or video camera senses what is going on near the center of the image. If the image is uniformly lit, then that reading is representative and everything goes well. In Mr. Siebold’s video the sky likely was much brighter than his face. The camera was fooled by that bright light, so it underexposed his face. Zooming in more so his body covered the metered area would have improved things. Positioning the camera higher and aiming it down so it didn’t see as much sky also would have helped. 

The exposure meter also assumes that the image area reflects 18% of the light falling on it, which  is about right for skin. But when you try to image a long skinny object, like a ski sitting on a background of snow, or a sword on black velvet, you need to rethink the exposure because an average will be wrong.    

As one commenter on the video noted, it looked like the sun was behind Mr. Siebold, so a reflector placed behind the camera could have been used to light up his face.

A scene in a film from 1997, The Fifth Element, has Professor Pacoli trying to decipher a message carved on the interior wall of an Egyptian temple. A small boy named Aziz is holding the top edge of a large rectangular brass tray angled to reflect sunlight onto the wall for him. Aziz is tired and keeps nodding off, so the professor repeatedly calls: “Aziz, light!” and the phrase found its way into the Urban Dictionary.         

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