22 March 2016

Pinhole camera six-month exposure

The University of Wisconsin-Madison holds an annual Cool Science Images contest, inviting campus researchers to submit interesting photos and videos.
"Using a pinhole camera made of an aluminum can, duct tape and photosensitive paper and positioning the device atop Sterling Hall from winter solstice to summer solstice, yields a symmetric chart of the sun's path across the sky. The lowest arc was the sun's winter solstice trajectory and the highest arc was the sun's path at summer solstice. Gaps between the arcs are days of overcast weather.
I'm amazed that the paper isn't totally bleached-out during a six-month exposure.  The sensitivity of the paper must be extremely low.  Very cool.


  1. Apparently (going by the explanation of the process on this page), the reason for the picture's not being overexposed is that it isn't developed. The exposure alone is sufficient for the photosensitive paper to show an image without the need for further treatment with chemicals. Cool!

    1. developing is way of fixing / stabilizing a photosensitive medium so it no longer reacts to light. because they are not developed, those solargraphs, as stated at that link, will eventually go black as they remain exposed to light. the url touts the ecologicalness of not developing the film. that is because the chemicals used to develop film can be less than environmentally friendly.


  2. those solargraphs are, in a way, showing the analemma, but not as well as an analemma photo.



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