829
understanding of the nature of ionic mobility, crystal
structures and quantum theory. Only a much-simplifi ed
explanation is, therefore, possible.
Since the end of the 19th century, most photographic
fi lms, plates and papers have been coated with a gelatin
emulsion in which are suspended crystals of light sensi-
tive silver halides (chlorides, bromides, and iodides). A
brief exposure of light is believed to act on some silver
halide crystals in a way that produces an aggregate of
metallic silver atoms. This aggregate is the latent image,
the invisible building blocks from which the visible im-
age is formed. The number of silver atoms involved may
be very small but they render the silver halide crystals
susceptible to the action of an appropriate chemical
solution, (developer), which when applied causes the
invisible aggregate to change and grow into a visible
image of black metallic silver. Although understand-
ing of the latent image has greatly progressed since the
19th century, its mechanism remains based on theory
and subject to modifi cation and revision. Even with the
best modern technology, it remains impossible to detect
a latent image by direct physical or chemical means.
John Ward
See also: Talbot, William Henry Fox; Daguerre,
Louis-Jacques-Mandé; Calotype and Talbotype;
Daguerreotype; and Photogenic Drawing Negative.
Further Reading
Arnold, H.J.P. William Henry Fox Talbot, Pioneer of Photography
and Man of Science, London, Hutchinson Benham, 1977.
Latent Image, Cassell’s Cyclopaedia of Photography, edited by
Bernard E. Jones. London, New York,. Cassell and Company
Ltd., 1911.
Latent Image, The Focal Encyclopedia of Photography, vol. 1,
London, Focal Press Ltd., 1965 (fully revised edition).
Mees, C.E. Kenneth, From Dry Plate to Ektachrome Film, New
York, Eastman Kodak Company, 1961.
Schaaf, Larry J. Records of the Dawn of Photography, Talbot’s
Notebooks P & Q Cambridge University Press, 1996.
Wood, R.D. “The Daguerreotype and Development of the Latent
Image: “Une Analogie Remarquable” in The Journal of Pho-
tographic Science. 44, no. 5 (1996): 65–167.
LAURENT, JUAN AND COMPANY
(1816–before 1892)
Born Jean Laurent in Garchizy, France, in 1816, he
moved to Madrid in 1843, where he reportedly regis-
tered himself as “Juan” (the Spanish style of “Jean”),
and established and operated a successful company
manufacturing cardboard packaging. His photographs
however, where they are identifi ed, simply bear the
legend “J. Laurent” or “J. Laurent y Cia.”
His earliest recorded encounter with photography
dates from 1856, with the establishment of a studio at
Carrera de San Jerónimo in Madrid. Although he lived in
Spain for the remainder of his life, he never lost contact
with his French roots and, at the height of his success,
Laurent opened a gallery in Paris selling prints from his
fi nest Spanish and Portugese architectural and landscape
scenes, copies of great paintings, art and architectural
treasures. Like the Englishman Charles Clifford, he
photographed and sold images of Spain’s rush towards
the modernisation of its capital city, and the building
programmes which dominated the 1860s.
Again like Charles Clifford, he went on to develop a
reputation as one of the fi nest photographers in the city,
enjoying, also like Clifford, the patronage of Queen Isa-
bella II. Indeed, for most of the 1860s, he styled himself
“Photographer of Her Majesty the Queen.”
Laurent’s large format camera work is technically
more precise than Charles Clifford’s—with great at-
tention to details of architectural accuracy—but like
Clifford, his love of the Spanish light, architecture, and
scenery is apparent. In some of his architectural stud-
ies, careful choice of camera position, ideal lighting,
and technical excellence combine to produce images
which revel in simple geometric patterns, a direct and
graphic style which others would adopt only very much
later. Puente de Zura (Collection of the Metropolitan
Museum of Art) dating from c. 1867, is a fi ne example
of this approach.
In 1867 the studio exhibited a number of large Ál-
bumes de Obras Públicas at the Exposition Universalle
in París, and the production of large albums of views
would remain a signature activity for the studio.
Laurent reportedly employed several photographers
to create the images for these albums and catalogues,
as well as a large number of support staff. One of the
photographers was José Martínez-Sánchez who worked
with Laurent for many years, and is believed to be
responsible for a signifi cant proportion of the studio’s
considerable output.
In 1866, in collaboration with Martínez-Sánchez,
Laurent perfected ‘Leptographic’ paper (‘Leptofoto-
grafía’), a collodio-chloride printing paper which was
sold ready to use. The light sensitive silver chloride was
held in a binding layer of cellulose nitrate, separated
from the paper by a layer of barium sulphate (later
known as baryta), giving a much whiter base colour to
prints than had been previously possible with albumen
paper. The baryta layer acted as a barrier, eliminating
the spotting from rusting metal particles in the paper
which sometimes happened with albumen papers, and at
a stroke, the introduction of this paper removed from the
photographer all the paraphernalia of having to sensitize
the paper before use, as had been needed with albumen.
As the manufacturers claimed, it had three times the
sensitivity of albumen, and exposure times for contact
printing could also be reduced signifi cantly. In the same