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work on polarisation. Fresnel discovered what was later
called circularly polarised light. No hypothesis led to
the experimental results obtained other than that light
is a transverse wave and, in 1821, Fresnel published a
paper in which he claimed with certainty that light is a
transverse wave. This went too far for most, even Arago,
but Fresnel stunned his critics when he next showed that
double refraction could be deduced from the transverse
wave hypothesis.
After 1824 he devoted less time to his researches on
light. He was employed by the Lighthouse Commission
and as part of his effort he invented so-called Fresnel
lenses which were made by splitting a large lens into
stepped concentric rings and mounting them in the same
plane. These quickly replaced mirrors for lighthouses
and lenses as large as 3 metres in diameter have been
constructed using this method. This invention has found
numerous other applications, including the lenses in
theatre lights, collimators in overhead projectors and
the lenses in the view-fi nders of SLR cameras.
Fresnel died of tuberculosis in on 14 July 1827 in
Ville-d’Avray, France at the age of 39. He had struggled
throughout his life against ill health but it is remark-
able that he was able to undertake an exceptionally
high workload despite suffering from severe fatigue.
Perhaps it was the strict religious upbringing by his
parents which gave him the strength to overcome his
illness for so long.
The unit of optical frequency has been named after
Fresnel. One fresnel is 1012 hertz (one terahertz).
John O’Connor
Edmund Robertson
Further Reading
Silliman, R. H., Biography in Dictionary of Scientifi c Biography.
New York, 1970–1990.
Details on Fresnel lenses can be found, for example at http://
en.wikipedia.org/wiki/Fresnel_lens.
FRESSON AND FAMILY, THÉODORE-
HENRI (1865–1951)
French inventor of carbon paper Charbon-Satin
Agronomist by profession, Théodore-Henri Fresson also
worked on electronics and with military technology.
In 1899 he presented before the French Photographic
Society “Photographic proofs printed on carbon paper
that can be developed without transfere.” His process
came from Charbon-Velour (Victor Artigue. 1889) com-
mercialised in 1893. The composition of the Charbon-
Velour Paper was a secret and so was the formula for
the Charbon-Satin (with the exception of the inventor
family, the photographer José Ortiz Echague and the
workshop Luis Nadeau in Canada).
By the 1900’s and thanks to the efforts of Maria, the
wife of Fresson, and their sons Pierre and Edmond, the
Charbon-Satin was manufactured and sold. Fresson’s
product was more reliable than the Artigue process it
was in competition with it.
Thereafter, the advent of small format negatives
forced Pierre Fresson to adapt the procedure for enlarge-
ments. From 1947, the Fresson brothers, aided by their
children (Micheline and Jacques for Edmond, Colette
and Monique for Pierre) achieved prints production
themselves in their workshop at Dreux. The sale of
monochrome prepared papers progressively decreased
around 1950. In response to this, Pierre Fresson, helped
by his son Michel, adapted the process to quadrichromy
(the fi rst process for the production of permanent colour
images). In the sixties, their main clients were adver-
tising photographers. Since the seventies, the ‘Atelier
Fresson’ has been prized by artists and photographers
such as John Batho, Bernard Plossu and Bernard Fau-
con. In 1978, the son of Michel, Jean François Fresson,
joined the team, continuing a one hundred year family
tradition.
Luce LebartFRESSON PROCESS
The genesis of this process takes us back to Alphonse
Poitevin’s carbon process of 1855, whose original
patents (Fr. Pat. 24,592, Aug. 27; the Engl. Pat. 2,816
of Dec. 13, 1855 is not as complete) covered both car-
bon printing and collotype. The carbon process takes
its name from the carbon black pigment that Poitevin
used in his early experiments. Any permanent pigment
mixed with potassium dichromate and a colloid such
as albumen, gelatin or gum arabic, will result in an
emulsion sensitive to light. Exposed under a negative,
a dichromated pigment coating will become insoluble
proportionally to the amount of light it receives. Parts of
the image which are protected by the dense areas of the
negative will remain water soluble and will reveal clear
highlights after development has taken place in cold or
hot water, as required by the nature of the colloid used.
This process, which does not involve a transfer of the
emulsion before development (unlike the carbon transfer
process), is referred to as “direct carbon.”
Few people used the original Poitevin direct carbon
process as the resulting images produced a short scale
with excessive contrast which most photographers
considered inferior to the silver prints of those days.
This technique remained largely dormant until it was
revived, under the name of gum printing, ca. 1894,
by Rouillé-Ladevèze in Paris. In the meantime direct
carbon was used for the reproduction of tracings and
architectural drawings and one particular variant, intro-
duced by Frédéric Artigue, around 1878 was adapted by