Green River Canyons, Utah
This very picturesque part of Utah was taken through the window of a commercial jetliner flying at about 30,000 feet elevation. The stunning contrast does not come straight from a digital camera, but considerable digital enhancements must be made. The original un-enhanced image is very hazy and bluish seen in the second image below. The bluish color seen from high altitude flights on clear days is the same phenomenon as the blue sky. Molecules of a pure gas do not have a uniform distribution, but there are microscopic fluctuations in the density of the gas molecules. These density fluctuations are responsible for scattering blue light more so than red light. That is why the sky is blue and snapshots from airplane windows look hazy, washed-out, and blue - even when there is no air pollution.
Professional aerial photographers alleviate the problem of
blue "overwash" by using infrared-sensitive film. This
way the invisible infrared light exposes the film and
suppresses the scattered blue. One can also use
specific-colored visible filters (yellow) that suppress the
blue. Polarizing filters (see
PPOW for Aug 27, 2010) are also very effective because
the blue overwash light is generally polarized.
Traditional haze filters - popular in film photography where
the film has a higher sensitivity to blue and near ultraviolet
- do not work with digital cameras because the image sensors
in digital cameras (unlike film) are not very sensitive to the
near-ultraviolet light. The methods in today's PPOW used
image processing software to enhance the red and green colors
while suppressing the blues (simulated filters).
The "loop" canyon in the center of the photos is called
Bowknot Bend in the Green River just north of Canyonlands
National Park. The canyons in the Colorado Plateau in
Utah and Arizona are also scientifically interesting and
featured in PPOW
for April 19, 2013.
Physics Photo of the Week is published weekly during the academic year on Fridays by the Warren Wilson College Physics Department. These photos feature interesting phenomena in the world around us. Students, faculty, and others are invited to submit digital (or film) photographs for publication and explanation. Atmospheric phenomena are especially welcome. Please send any photos to firstname.lastname@example.org.
All photos and discussions are copyright by Donald Collins or by the person credited for the photo and/or discussion. These photos and discussions may be used for private individual use or educational use. Any commercial use without written permission of the photoprovider is forbidden.