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Various

"Scientific American Supplement, No. 430, March 29, 1884"


In face of the progress made by extra rapid dry processes, the question
of shutters has become the most important, since cabinet-making, optics,
and photographic chemistry give us apparatus, objectives, and products
which, although they will doubtless be improved upon, satisfy for the
present all our needs.
What is understood by instantaneousness? To our knowledge, no definition
thereof has as yet been given. For our part, we propose to style
"instantaneous" any photograph that is taken in a fraction of a second
that our senses will not permit us to estimate. The shutter is the
apparatus which allows the light to enter the photographic chamber
during this very short time.
In order to examine the different rules that govern the question of
shutters, we shall take as an example the type styled the "Guillotine."
This apparatus, as every one knows, is a stiff plate containing an
aperture and passing over the line of the rays of light. Some place
it in front and others behind, while others again place it within the
objective.


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