Camera steadiness test
[Film Technology]
Sophisticated
means existing accurately checking and measuring image
displacement. But a practical method used by most camera mechanics is to
photograph a grid or radiating
pattern of lines with the camera rigidly mounted on a particularly
robust stand, then to rewind the film and
expose it again, displacing the camera slightly, horizontally and vertically.
When film has been processed, any unsteadiness shows up as relative movements
between the two exposures. This is the only way
of pinpointing a camera fault. By using a pattern consisting of a series of
radiating black and white lines a ‘chrysanthemum’, double exposed image unsteadiness will show as a moiré pattern and may be readily discernible on the screen. Another system uses cranked
lines which are reversed between takes thus giving an arrow like pattern
from which unsteadiness may not only be seen but also quantified. The degree of
image steadiness to be expected of a camera vary according to the make, type, state of
serviceability and frames per second rate
required. A simple camera movement employing a pull-down
claw only can never produce image as steadily as a camera with double pull-down claws on each side and double close register pins. Some cameras are
acceptably steady-at 24-60fps but not at 80 fps while others, in good
condition, can be expected to be steady, even for double
exposure process printing, at 128 fps.
e-mail: pratheepvasudev@gmail.com
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