Spider Web Spectrum
December 16, 2007
The thin linear threads of spider webs occasionally act as optical slits, decomposing white light by diffraction. The resulting colors aren't as pure as those of refraction phenomena, as in a rainbow or in an ice halo. This is because each wavelength generates a distinct periodical spatial pattern, and what we see is thus the result of overlapping colors (wavelengths). Iridescent clouds also result from diffraction of sunlight. The diameter of the minute water droplets composing mid-level clouds is similar to the diameter of spider web threads -- a few microns or even less.
Photo details: Canon EOS 350D camera with a 70-300 mm APO DG Sigma lens set to a focal length of 263 mm. Exposure time of 1/60 second with aperture at f/6.6 and film speed of ISO 100.