of the reflector. Therefore, 1.5 feet must be added to the measured
distance between the stroboscope and subject. For example, if this dis -
tance is 2 feet, use 3.5 as the number to be divided into the guide number
to obtain aperture setting.
The guide numbers shown in Figure 2-5 should be regarded as only
a tarting point for obtaining correct exposure. Contrast between subject
Figure 2-6. Guide number correction for repetitive
flashing with a Type 1531 Stroboscope.
and background, type of film, development techniques, and many other
variables should also be taken into consideration. Trial photographs are
most helpful in determining optimum exposure. Follow the film manu -
facturer's recommendations when processing the film.
For detailed information on the use of the stroboscope for photo-
graphic applications, refer to General Radio's "Handbook of High -Speed