CAS 522 Camera Obscura

  Around 1976, then curator of the Astronomy Department Jeffrey Baumgardner noticed that if the window in our planetarium was cracked open, the room acted as a camera obscura.  As the open window was a slit it was a rather poor camera opening, so he proceeded to carve a hole (elliptical, to work better on the dome) and our camera obscura was born.  Around 1980, Prof. Brecher transferred the camera obscura to our large classroom (CAS 522) using a circular opening.   A diaphragm can be used to sharpen the image (by closing it) or brighten the image (by opening it).

  Just what is a camera obscura?  See the wikipedia entry for a decent explanation.

  Recently the now curator Quinn Sykes and I (the in-between curator), took some photos of the room, presented here.    Each setup is presented three ways: lights on, lights off, and rotated and flipped to appear as if would were you looking out the window.  Click on the thumbnails to see the images more clearly.

  For those interested in the details, the images are all taken with a Canon 20D camera using a Canon EF-S 10-22mm lens.  The camera was mounted on a tripod, and the darkened room exposures were 30 seconds long at f/6.3.   I shot the images in raw mode, brightened them by 2 stops when loading them, and processed them a bit to reduce the noise, although you can still see plenty.   The last two images, primarily of the ceiling, are rather distorted as the camera (and the ceiling) is quite close to the opening.

  Once you are dark adapted the image is plainly visible to the naked eye, but they do not appear this bright. For some reason I always find it startling that the images move - cars pass by and pedestrians cross the parking lot.  Unfortunately my still camera can't catch this for you.

  To demonstrate the process a little more clearly I created some morphs of the room changing from lights on to lights off - these are presented as animated GIF's and AVI animations. 

GIF	AVI