February 22, 2005
Time Lapse Animations from HPWREN Cameras show Interesting Cloud and Fog Formations
The recent rains in San Diego County were an opportunity to
observe interesting cloud and fog formations. An example is the camera
installation described in
http://hpwren.ucsd.edu/news/041221.html. This IQeye3 camera
uses a monochrome imager and does not have the cyan filter that
"normal" cameras have to keep them from near-infrared sensitivity. In
addition, the camera has a 900 nanometer bandpass filter in front
of its lens. Hence the imager only sees around 900 nanometer,
which is near-infrared and invisible to humans. When looking through
the lens filter of the camera, it appears totally dark to the human
eye. In the case of blue sky, the sky looks almost black, due to
the lack of heat. The clouds diffuse the sunlight, and hence appear
white. Live green vegetation appears white, as it reflects
some infrared. Dead or dying vegetation is far less reflective in that
part of the light spectrum.
Various time lapse animations have been created from imagery, available at http://hpwren.ucsd.edu/Animations/. These files are usually large and require significant bandwidth and patience to download. It is recommended to save the files onto the local computer and run them locally, rather than across the network. Most of the files are in DVD-compatible MPEG2 format for NTSC, with a four megabytes-per-second variable rate that can burst to seven megabytes-per-second.
Other pointers at
http://hpwren.ucsd.edu/Animations/ show videos from various
locations and times, several in time-lapse format.
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