Upward and Downward Shadows
June 10, 2012
Photographer: Mario Freitas
Summary Author: Mario Freitas
Walking among some old trees in Sao Lorenco Park, Curitiba, Brazil, I noticed the curious optical effect shown above. One photo shows my shadow falling on the trunk of an old Parana pine (Araucaria angustifolia) tree. In the other photo, my shadow is cast on the ground. Geometric optics explains the difference: in the photo on the left (upward shadow), the sunbeams responsible for the shadow have reflected off a pond surface whereas in the photo on the right (downward shadow) no reflection was involved. Note that I shifted my body leftwards in the downward shadow photo in order to allow the direct shadow to be cast on the ground. The photos were taken three minutes apart while I waited for a cloud to move away from the Sun. At the time the Sun was elevated about seven degrees above the horizon. A similar effect to this can be seen when rainbows are reflected off water surfaces, creating a reflection bow. Photos taken June 2, 2012.
Photo details: Left - Camera Maker: Panasonic; Camera Model: DMC-LX5; Focal Length: 5.1mm (35mm equivalent: 24mm); Aperture: f/2.2; Exposure Time: 0.010 s (1/100); ISO equiv: 80; Exposure Bias: none; Metering Mode: Matrix; Exposure: program (Auto); White Balance: Auto; Flash Fired: No (enforced); Orientation: Normal; Color Space: sRGB; Software: ACD Systems Digital Imaging. Right - The same except: Aperture: f/2.0; Exposure Time: 0.017 s (1/60); ISO equiv: 100.