It follows that the shorter
the exposure is, the greater becomes such value, and to such a point
that, at a given moment, the apparatus no longer make an exposure.
[Illustration: FIG. 4.]
In the guillotine, on the contrary, the same space always intervenes
between the time of opening and closing, since it is fixed in an
unvarying manner by the diameter at the aperature. Then, the greater the
velocity, the more the time of opening and closing diminishes. If
the ratio of the effective to the total time of exposure is 3/4, for
example, it will be invariable, whatever be the velocity.
In concluding, we will remark that, without employing springs, we
may increase the aperture of the shutter without varying the time of
exposure. To effect this it is only necessary to raise the point of the
shutter's drop. In fact, as may be seen in Fig. 4, all the vibrations
of the stylet corresponding to 1/100 of a second always continue to
elongate, and it will consequently be possible for the same time of
exposure to considerably increase the aperture and, as a consequence,
the effective time, by causing the guillotine to drop from a greater
elevation.
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