Problems of Scale

August 05, 2011

JohnAreedsP4300058 (3)

Photographer: John Adam; John's Web Site
Summary Author: John Adam

Is this an aerial photograph of a logjam, a raft of reeds swept into the corner of a jetty by a combination of wind and currents, or a poorly thatched roof on a cottage in the south of England? The mere fact that there is some ambiguity about the picture indicates that there’s a problem: the problem of scale. How large are the logs, reeds or fibers in the picture? What is the size of the field of view? If something of known size such as a rowing boat, life raft or beer mug (depending on context) had been included in the picture, the ambiguity would disappear. As it happens, the photograph shows a raft of reeds accumulating in the corner of a small jetty or side-water in Sandbridge, Virginia. The area shown is about 10-12 sq ft (about one sq m). A subsidiary question, independent of context is this: about how many reeds are there in the picture? Several hundred? Several thousand? Estimation techniques such as apply here can be used to gauge the size of crowds, herds of wildebeest on the African veldt, or blood cells on a microscope slide. Photograph taken on the afternoon of April 30, 2011.

Photo details: Camera Maker: OLYMPUS IMAGING CORP.; Camera Model: SP570UZ; Focal Length: 17.1mm; Aperture: f/4.0; Exposure Time: 0.013 s (1/80); ISO equiv: 125; Exposure Bias: none; Metering Mode: Matrix; Exposure: Creative Program (based towards depth of field); White Balance: Auto; Flash Fired: No (enforced); Orientation: Normal; Color Space: sRGB.