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Exploring Photography
especially if there is any movement. Exposure
times are long. But, the pinhole camera dem-
onstrates how simple photography can be.
Web site
www.pinholeday.org
On the last Sunday of April each year
photographers take pictures with a pinhole
camera. You can post one of these photos to
the website to share with visitors all over the
world. Worldwide Pinhole Photography Day
was created to promote and celebrate the art
of pinhole photography.
Kinds of Lenses
The pinhole can be replaced with a simple
lens. See Figure 3-8. Since more light can enter
the camera, exposure time is reduced. However,
a shutter is now needed to control the light.
Exposure using a small opening Exposure after pinhole has been enlarged
Figure 3-7. Pictures made with a pinhole camera.
Figure 3-8. A simple lens is more practical than a
pinhole. The lens allows more light to strike the fi lm.
Figure 3-6. A pinhole camera produces an upside-
down image on the fi lm.
The shutter is placed in or behind the lens,
and can be opened for carefully measured
lengths of time. Light falling on the fi lm or
digital sensor can be controlled to fractions
of a second.
Light striking the surface of an object is
called incident light. See Figure 3-4. A light
ray passing through a sheet of glass changes
its path as it enters the glass. However, the
light ray will exit, traveling in the same direc-
tion as when it entered. See Figure 3-9.
This only happens when the glass sur-
faces are parallel. If the surfaces are not par-
allel, as in a prism, the rays will be refracted
or bent at each surface. See Figure 3-10.
Most inexpensive cameras have simple
lenses. The simple lens can he compared to two
prisms placed base-to-base. See Figure 3-11.
Notice how the light rays pass through the
prisms. The rays do not converge (come
together) at the same point.
However, by rounding the prisms, the
rays passing through the lens are made to