Re: Pinhole camera

[Leigh Palmer <palmer@sfu.ca>]

> 	I think a point concerning the mapping may have been missed.  It
> is a mapping from one space (Not a plane) into another space.  A pinhole
> because of its infinite depth of field maps all of the object space on to
> the plane of its screen, but the screen can be in an infinite number of
> positions.  Thus any point in the object plane is mapped to an infinite
> number of points in the image space and vice versa. (All assuming perfect
> geometric optics.)

It is my understanding that a pinhole camera is a box; the screen is an
integral part of the camera. Without the screen the pinhole alone forms
no image. The percept of an object is only accomplished when the screen
is present. The question you are really asking is "Does a pinhole form
an image?" By my definition the answer is "No."

The pinhole camera itself is quite a varied thing. In 1991 I helped a
colleague construct a pinhole mirror solar telescope to view the solar
eclipse in Guatemala City. In this variant a small mirror is positioned
so as to reflect the Sun's rays onto a screen in the shade, in that
case in a relatively unlit corner of an external walkway at his college.
It worked quite well, and the weather did cooperate for the eclipse,
which I watched from Costa Rica, where the weather was also favorable.

Another variant is the coded aperture mask camera which another member
of this group is better qualified to discuss than I. In that camera
many pinholes are used instead of just one. The effect is a reduction
in the exposure time required.

Leigh