Such a result is contrary to all photographic
rules, which require that objects shall pose so much the longer the
less they are lighted. This position of the "guillotine" shutter is
absolutely false, and must be altogether discarded. If the shutter be
placed behind the objective, it will follow, as a consequence of the
same demonstration, that the time of exposure will go diminishing from
B' to A', and that the foreground will be exposed longer than the sky.
The solution is logical, then, and will permit of obtaining excellent
negatives.
[Illustration: FIG. 1]
Let us now examine how the image, A'B', is formed. The point, A, appears
first, and becomes lighter and lighter up to the moment at which all the
rays that emanate from the point, A, are unveiled. The point, B', is not
yet visible. As the shutter continues its travel the point, B', appears
in its turn and becomes illuminated like the point, A'. At this moment
the objective is completely uncovered; the image, A'B', is perfect, and
possesses its maximum intensity.
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