Unlike most major inventions, photography had been long and impatiently awaited.
The images produced by the camera obscura, a boxlike device that used a pinhole
or lens to throw an image onto a ground-glass screen or a piece of white paper,
were already familiar - the device had been much employed by topographical artists
like the Italian painter Canaletto in his detailed views of the city of Venice. What was
lacking was a way of giving such images permanent form. This was finally achieved
by Louis Daguerre (1787-1851), who perfected a way of fixing them on a silvered
copper plate. His discovery, the "daguerreotype," was announced in 1839.
A second and very different process was patented by the British inventor William
Henry Talbot (1800-1877) in 1841. Talbots' "calotyp" was the first negative-to-
positive process and the direct ancestor of the modern photograph. The calotype
was revolutionary in its use of chemically treated paper in which areas hit by light
became dark in tone, producing a negative image. This "negative," as Talbot
called it, could then be used to print multiple positive images on another piece of
treated paper.
Q. According to paragraphs 2 and 3, which of the following did the daguerrotype
and the calotype have in common?
A. They were equally useful for artists.
B. They could be reproduced.
C. They produced a permanent image.
D. They were produced on treated paper.
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