Pinhole Demonstration April 5, 2012

Joshua Dunn will demonstrate and the pinhole camera and it's many variations.
George L. Smyth will display prints from the sieve pinhole variation.


Following the presentations there will be a gear swap and print sharing. 


http://www.pinholeday.org/support/?pid=faq by Larry Bullis


Pinhole photography is similar to "common photography" in most respects but differs in that the camera used has no lens. Instead, it has a very small aperture which projects an image upon the sensitized material (film or paper). This necessitates different ways of working (primarily because the exposures must be relatively long) and produces images which differ from lens images in several important respects.

Where a lens forms an image by bringing rays of light coming to it from each point in the subject to a common focus, the pinhole does not focus at all. Instead, it acts as a center of projection.

Speaking practically, a ray of light from any point in the subject, passing through the pinhole, will intersect the film in only one place. Another ray of light, coming from a different point in the subject and passing through the hole will strike the film in a different place. The accumulation of all rays of light passing through the hole will thus form an image at the film plane. If the film plane were moved forward or backward, the image would still be there, but it would be smaller or larger depending upon where it were located.

Because the hole is actually not truly a point, it allows more than just one ray from each point in the subject to strike the film. We could say that it passes a small bundle of rays from each point. This is one reason why pinhole images are characteristically softer than lens images. The other reason is that some of the rays encounter the edge of the hole and are diffracted; they bend.

Since there is no focus, the sharpness of the image (such as it is; it is always somewhat "soft") is uniform from near distance to far. In other words, there is no limitation of depth of field as there is in lens photography. Very near objects (closer than the pinhole to film distance) will however become softer due to divergence of the rays coming from each point.

Information and Links:

Worldwide Pinhole Day is April 29, 2012 (the last Sunday in April)
http://www.pinholeday.org/org/

Wiki on Pinhole: 
http://en.wikipedia.org/wiki/Pinhole_camera