In the very earliest days of photography this term was applied to what
would now be considered very slow work indeed. We now usually apply
this term when the exposure does not exceed one second. In some cases
this only amounts to the one-thousandth part of a second. This
exceedingly brief exposure is usually given to the plate by means of a
suitably constructed shutter.
The immense strides that have recently been made in instantaneous
photography, owing chiefly to the advent of the dry-plate process,
have caused photography to become useful to almost every branch of
science.
To Muybridge and Anschutz we are greatly indebted for the strides made
in instantaneous photography. These gentlemen have succeeded in
photographing moving objects hitherto considered impossible to be
photographed. Galloping horses, swift-flying birds, and even bullets
and cannon balls projected from guns have been successfully
photographed, showing even the little head of air driven along in
front of the bullet.
[Illustration: FIG. 79.]
Both Muybridge and Anschutz also succeeded in making series of
twenty-four or more photographs of a horse during the time it makes a
single leap, and thus illustrated its every movement. The value of
these and other possibilities with the camera for artists cannot be
overestimated. Its aid to meteorologists in photographing the
lightning, to astronomers in stellar, lunar and solar photography, and
to all other sciences would require a work as large as this to
describe.
[Illustration: By Lt. Joachim Steiner. FIG. 80.--INSTANTANEOUS
STUDIES.]
For the making of instantaneous pictures a large number of suitable
cameras have been devised. In most of these the lens is a very rapid
one, and in some cases so arranged that all objects beyond a certain
distance are in focus. With an instantaneous camera a secondary image
is necessary, so that the right second can be judged for making the
exposure. This is usually produced by a finder. In making
instantaneous exposures the following tables may be useful:
Approximate distance
feet per second
A man walking 3 miles per hour moves 4-1/2
A man walking 4 miles per hour moves 6
A vessel traveling at 9 knots per hour moves 15
A vessel traveling at 12 knots per hour moves 19
A vessel traveling at 17 knots per hour moves 28
A torpedo boat traveling at 20 knots per hour moves 35
A trotting horse 36
A galloping horse (1,000 yards per minute) 50
An express train traveling at 38 miles an hour 59
Flight of a pigeon or falcon 61
Waves during a storm 65
Express train (60 miles an hour) 88
Flight of the swiftest birds 294
A cannon ball 1,625