Handbook of High Speed Photography - IET Labs, Inc.

made with the same camera without readjustment. Use of full-bellows
extension will produce an image magnification in the camera. High
speed films are employed to permit a minimum aperature setting for
maximum depth-of-field and/or shorter flash duration for reduced blur.
1 YARN TRAVEL
Figure 5-15. Setup used to photograph false-twist spindle.
DETAILED PROCEDURE. The system is assembled as indicated in
Figure 5-15 and tested for proper operation. The photo pickoff gener
ates the synchronizing signal directly from a reflective stripe on the
spindle. Reflective tape is not suitable here because of the centrifugal
force to which it would be subjected. The spindle is polished with
crocus cloth and all but a narrow strip blackened with a felt-tipped
marking pen. With the Delay Unit toggle switch at MULTIPLE, the
pickoff is positioned near the spindle to provide reliable triggering.
The camera is set up and focused, and the delay adjusted to orient the
spindle properly. The blur angle to be expected may be calculated as
follows for 3-microsecond flash duration:
250,000
60
revolutions
minute
seconds
minute
X360 defee X3X10"6 sec =4.5
revolution
The blur angle will be correspondingly smaller for shorter flash
durations, but since the photograph is of a "face" of the spindle, the
calculated blur is perpendicular to the plane of the film and is negli
gible.
Test pictures may first be taken using a Polaroid adaptor loaded
with ASA 3000 (type 57) film. The corresponding guide number for the
1538 Strobotac operating in the high-intensity range is 90 (from Figure
56