705
photography was potentially a great creative art, and
that it did not need to be bund down to rule set up for
painting. ‘Naturalism’ he wrote, ‘is an impersonal
method of expression, a more or less correct refl ection
of nature wherein’ truth of sentiment, illusion of truth
of appearance (so far as is possible) and decoration are
of fi rst and supreme importance.
Emerson sought a scientifi c basis for pictorial photog-
raphy. He analyzed the physiology human perception.
He reasoned that since the eye sees distinctly only a
small part of what lies before it, while the surrounding
area appears indistinct, it should be possible to repro-
duce this phenomenon by controlling the focusing. Only
a small part of the photograph should be sharp, the rest
should be just slightly out of focus. Today we recognize
that this theory of vision is fallacious, because the eye,
unlike the lens of a camera, is a living organism, which
scans the fi eld of view constantly in such a way that the
mind receives a composite report and the impression of
full detail. The naturalistic theory was an advance over
Newton’s; for Emerson believed that the photographer
should rely entirely on controls which were they part of
the photographic process. In addition to control through
differential focusing, he advised the careful use of de-
veloping and printing methods.
Emerson took a large number of photographs of
the amphibious life of the simple country folk on the
Norfolk Broads, which were entirely different of the
artifi cial genre studies of Robinson and very close to
the graphic work of J. F. Millet, which Emerson greatly
admired. Imbued with a deep artistic feeling, Emerson’s
photographs fi red a number of other amateurs to seek
inspiration in nature as the fi rst generation in limited
editions in handsome folio volumes as original platinum
prints or as photogravures and photoetcings.
There was a profound shift in the perception of
photography around 1890. Discussions of photography
were largely qualitative, e.g. is it an art or a science?
The science of photography was largely of an alchemical
sort. The scientifi c questions were also qualitative, due
to the failure of photographic “evidence” to fi t existing
theories of the behavior of light. Were there new “im-
ponderables” (phenomena without mass) to contend
with besides light, heat, magnetism, and electricity? The
questions were ones of kind, not relationship. That is,
until Hurter and Driffi eld.
James Clerk Maxwell suggested in 1862 that mag-
netism, electricity, and light were all manifestations of
a larger electromagnetic spectrum. However, it wasn’t
until he published Electricity and Magnetism in 1873
that the idea began to take hold. Suddenly, the questions
asked about the behavior of photosensitive materials
took a different form. They became mathematical in
nature: what was the relationship between exposure to
light and photographic material? Instead of questioning
the qualitative nature of light, as researchers such as
Hunt and Draper had done, researchers began to look
for better methods of measuring light quantitatively
and exploring the relationship between exposure and
response in photographic materials.
Film speeds were fi rst scientifi cally measured around
the 1880s to 1890s with initial work by Sir William Ab-
ney but continued and published in 1890 by Ferdinand
Hurter and Vero Driffi eld, working at the centre of the
UK chemical industry in Widnes.
The birth of photography as a modern science seems
to have occurred circa 1880, with the invention of the
actinograph (light meter) by Hurter and Driffi eld and
the fi rst motion studies of Muybridge. Both these efforts
were carefully measured and mathematical in nature.
The intense period of experimentation in the 1880s was
fueled both by a technological need and a desire to have
proof of a measurable nature. The shift during this time
from relatively forgiving wet plates and the more tricky
but convenient dry plates was part of the equation—pho-
tographers needed better instrumentation than “rules of
thumb” to get consistent exposures. However, the one of
the fi rst uses of the actinography was to mathematically
establish the relationship between the position of the sun
in the sky to light intensity. Motion studies were used to
establish the relationships between muscle groups and
motion, rather than to create more accurate depictions of
motion. At issue in both types of research were matters
of detection rather than depiction.
The culmination of Hurter and Driffi eld’s research
was the characteristic curve used to measure photosensi-
tive materials—named the H&D curve in their honor.
With the discovery that there was a mathematical rela-
tionship between exposure, development, and density in
photosensitive materials in 1890, photography became
scientifi c in the modern sense. Their work plotted im-
age density against the logarithm of exposure, produc-
ing what became known as ‘H&D’ or ‘characteristic’
curves. These curves had a straight line section which
could be extrapolated back to the density axis to give a
speed point that could be used to compare materials, and
speeds based on these were known as ‘H&D’ speeds.
Around the same time, Jules Scheiner in Germany
introduced a cruder method based on the minimum
exposure required to give a perceptible image in 1894.
The work of Hurter and Driffi eld was extended by the
German company Agfa in the 1920s to incorporate the
less steep portion of the curve at lower exposures to
produce a more practical measure accepted as a na-
tional standard (DIN) in 1931. The Weston Company in
America introduced their own speed system designed to
work with the integrated light readings of their famous
exposure meter in 1932 (WESTON). Similar consider-
ations and the increasing deviation of modern materials
and developers from straight line responses led to theHISTORY: 8. 1890s