Nonlinear Projections - Transformations and Projections in Computer Graphics - page 184

A rotating camera, as its name implies, works by rotating on its base, transferring
the image to the film while moving the film in the opposite direction, so the film stays
stationary relative to the ground. Examples of this type are the Swiss-made RoundShot
[roundshot 05], some of whose models are digital, the Globuscope [Globuscope 05], and
the Hulcherama camera, invented and built by Charles A. Hulcher [hulchercamera 05].
Following is some information on the latter type.
The Hulcherama is a slit-scanning panoramic camera that works by rotating on its
base. An electronically controlled motor is responsible for uniform rotation. (The rate
of rotation may be varied from 1 s to 144 s per revolution.) During the rotation, the
image passes through the lens and then through an adjustable narrow slit onto the film
(Figure 4.38a). The slit masks out most of the image but lets a narrow portion pass
through, which is how any optical distortion is minimized. As the camera rotates in one
direction, the film moves past the slit in the opposite direction. The camera rotation
and film movement are synchronized so that the film is stationary relative to the image
being photographed. As the camera makes a complete revolution, 8.9 inches of film
pass behind the slit, creating a 360 ◦ panoramic image with a height of 2.25 inches.
Theaspectratioisthereforeapleasing2 . 25: 8 . 9

1: 4. It is possible to let the camera
rotate more than one revolution (possibly varying the image each time), and a roll of
120-format film is long enough for three revolutions (the Hulcherama uses standard 120
or 220 roll film).

≈

sec. mirror

a

L

slit

slit

hinge

L

film camera

m

(a) (b) (c)

Figure 4.38: Panoramic Cameras.

A swing-lens camera (Figure 4.38b) has a lens that rotates during an exposure,
thereby “painting” the image on the film through a narrow, vertical, constant-width
slit. In order to keep the same distance between the film and the lens, the film has
to be curved. An advantage of this type of camera is that the lens only has to cover
the vertical dimension of the film and the width of the slit, so it does not have to
be complex. The downside of this type is the limited field of view, which is less than
180 ◦ . A complete 360 ◦ panorama is created by taking several shots and combining them
using special equipment (for a film camera) or special software (for a digital camera).
Examples of this type are the Widelux (now discontinued) and the Noblex.