Metal Fencing Patterns and Colors

May 11, 2014

HansCoherrentBackscatter1

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Photographer: Hans Juergen Heyen
Summary Authors: Hans Juergen Heyen; Jim Foster

Shown above is a wire-mesh fence with an iridescent sheen. When the Sun was behind me at a certain angle, the metal suddenly began to sparkle so that the fencing looked completely different than the photo at left. The slightest movement seemed to change the pattern, often quite remakably. This
is because in places sunlight is blocked and elsewhere it filters through the fencing. Thus the fence holes or openings are periodically in-line or out of line, so the conditions for alignment or transmission occur only periodically. This is known as a moire pattern. Note that this fence protects the entrance to the A44 motorway. Photos taken on the afternoon of February 2, 2014.

Photo details: Top - Camera Model: Canon EOS 600D; Lens: EF300mm f/4L IS USM +1.4x; Focal Length: 420mm; Aperture: f/9.0; Exposure Time: 0.0013 s (1/800); ISO equiv: 400. Bottom - Same except: Lens: EF-S18-55mm f/3.5-5.6 IS II; Focal Length: 55mm; Aperture: f/8.0; Exposure Time: 0.0063 s (1/160); ISO equiv: 100.