Handbook of High Speed Photography - IET Labs, Inc.

the relative position of these markers can often be discerned in a
photograph that would otherwise be useless.
When it is necessary to remove the stroboscope reflector in
order to illuminate hard-to-reach spots, the drop in light concentration
often is a problem. Ordinary household aluminum foil, when carefully
smoothed on a flat surface and attached to one side of the flash lamp
with clear cement, serves as a miniature reflector to minimize this re
duction. Be sure the flash lamp is clean and the brightest side of the
foil is placed toward the inside of the lamp. Best results are usually
obtained when the foil covers about half of the lamp between the two
spark electrodes, as shown in Figure 4-6;
Figure 4-6.
Application of an auxiliary
reflector to the Strobotron.
4.6 SHADOWGRAPH PHOTOGRAPHY WITH A SCOTCHLITE SCREEN.
Shadowgraph photography is a technique used to study intense
shock waves and fluid disturbances. Dr. Harold Edgerton has described
a technique for taking such photographs using a Scotchlite screen as a
reflective backdrop. For good definition with this method, an intense
point light source must be located as close to the camera lens as pos
sible. The Strobotac is ideally suited for this application since the
Strobotron spark discharge gap closely approximates a point light
source when directed as shown in Figure 4-7. Because of this, the
light output can be concentrated optically into a high-intensity beam
for special applications.
The bare Strobotron lamp is positioned next to and slightly be
hind the camera lens as shown in Figure 4-8, so that light is reflected
from the screen back through the subject plane and onto the film.
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