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one sheet, which became the database for a patented
exposure calculator, the Actinograph. From 1888 to
1892, Driffi eld sold the device from Widnes until the
photographic specialists, Marion and Company, Lon-
don, took responsibility for marketing it.
The Actinograph’s instructions explained how to fi nd
the rapidity of photographic plates, and make use of it
as an actinograph number. The procedures had evolved
from theoretical work carried out by Hurter, and cor-
roborated in practical experiments by Driffi eld. Hurter
reasoned that a photographic plate was inert to the action
of light until suffi cient energy overcame its inertia and
by converting this parameter to a number, it indicated
rapidity, or the fi lm speed. Because it was feasible to
measure all commercially available gelatino-bromide
plates, Hurter and Driffi eld advocated the merits of
accurate camera exposure and decried the prevalent
rule-of-thumb approaches.
During 1888 and 1889, the two men collaborated in a
further series of experiments and presented the results of
their investigations to the Society of Chemical Industry
in May 1890. It had been necessary to build equipment to
give controlled exposures to photographic plates and to
design apparatus to measure the photographic deposits
of silver, for which they introduced the term “density.”
By plotting their test results as a diagram (the H & D
curve), they characterised the parameters of different
plates, and determined their speeds. Hurter and Drif-
fi eld also examined the effects of exposure, variations
in development, the behaviour of developers, and the
criteria for the theoretically perfect negative.
The photographic community welcomed the compre-
hensive nature of Hurter and Driffi eld’s investigations,
but one important conclusion contradicted the perceived
wisdom of the time. They claimed errors in exposure
could not be corrected during development, and this
assertion outraged many contemporary commentators.
Hurter and Driffi eld were later criticised for using the
government-approved standard candle for testing plates
intended for use in daylight, and for selecting ferrous
oxalate as the standard developer, instead of a pyrogal-
lol-based type. Because their resources were commit-
ted to defending a controversial doctrine, the potential
benefi ts of the Actinograph, and actinograph speeds,
were overlooked.
Twelve months after Hurter and Driffi eld had an-
nounced their conclusions, an enthusiastic amateur
photographer, John Sterry, alerted Marion and Company
to the merits of Hurter and Driffi eld’s technique for
determining the sensitiveness of photographic plates.
In September 1891, he disclosed to Driffi eld that “the
partners are now thoroughly interested in adopting the
test methodology.” Ten years earlier, the Editor of The
British Journal of Photography, had encouraged Alex-
ander Cowan, (the manager of Marion and Company’s
Southgate works), to establish a reliable standard of
sensitiveness. Despite the initiative failing, Cowan had
continued to seek a test method for quality control in
the manufacture of plates.
The manager of Marion and Company’s London of-
fi ce, Frank Bishop, also identifi ed the marketing benefi t
in providing numerical values to indicate the rapidities
of each of the company’s four brands of plates. With
Driffi eld’s help, Sterry convinced Messrs Bishop and
Cowan, and Marion and Company announced the ini-
tiative would commence in 1892. Advertisements by
the company in The British Journal Almanac for 1893
explained that after “more than twelve month’s expe-
rience in testing by the Hurter and Driffi eld method,
we are in a position to state its absolute correctness.”
At the time, the speeds continued to be expressed in
actinograph numbers.
Within two years, as plate making techniques im-
proved, other manufacturers showed interest in the
methodology, which was now being used by Marion
and Company to determine H & D numbers. James
Cadett (principal of Cadett and Neall) also recognised its
worth, but he and Alexander Cowan realised a limitation
was the reliance on the standard candle as the exposing
source. Driffi eld had selected it on grounds of economy
and because it had been approved by Act of Parliament
in 1860 (for monitoring the quality of coal gas).
Hurter and Driffi eld agreed to replace the candle
with gas-powered lamps, which were a better match
for daylight and better suited to the examination of
orthochromatic and panchromatic emulsions. During
1896 and 1897, Driffi eld also resisted arguments that
the ferrous oxalate developer should be replaced by a
pyro-based one. In a lecture to The Royal Photographic
Society in January 1898, during which they received the
Progress Medal, Hurter and Driffi eld announced impor-
tant concessions and thus consolidated the acceptance
of the H&D Speed System.
Hurter died eight weeks later, and his partner declined
to undertake any further research in photography. Drif-
fi eld applied himself to his career in the alkali industry
but devoted his leisure time to practical photography
and Widnes Photographic Society, of which he was a
founder member. At the start of the 20th century, the
H&D Speed System was a recognised guide to fi lm
speeds, and retained a currency in parts of Europe until
the outbreak of the Second World War.
Following Driffi eld’s death in November 1915, The
Royal Photographic Society acquired his experimental
notebooks, letters and papers, which included those of
his late partner, Ferdinand Hurter. The material was
sorted and arranged by William Bates Ferguson as The
Driffi eld Bequest.
Ron Callender