An actinograph is an instrument for measuring or estimating the amount of light available, in terms of its ability to expose
photographic film
Photographic film is a strip or sheet of transparent film base coated on one side with a gelatin photographic emulsion, emulsion containing microscopically small light-sensitive silver halide crystals. The sizes and other characteristics of the ...
. That is, it measures the ''actinic'' or ''chemical'' intensity of light, as opposed to
radiometric
Radiometry is a set of techniques for measuring electromagnetic radiation, including visible light. Radiometric techniques in optics characterize the distribution of the radiation's power in space, as opposed to photometric techniques, which ch ...
or
photometric amount of light.
The earliest actinographs were 24-hour recording devices, using a rotating cylinder of photographic paper exposed through a wedged-shaped slit to record a graph of actinic light during the period of a day; hence the ''graph'' suffix in ''actinograph''. Such devices were developed and described by
Robert Hunt, secretary of the
Royal Cornwall Polytechnic Society
The Royal Cornwall Polytechnic Society (commonly known as The Poly) is an educational, cultural and scientific Charitable organization#United Kingdom, charity, as well as a local arts and cinema venue, based in Falmouth, Cornwall, England, Unite ...
in 1845, as an improvement on T. B. Jordan's 1839 ''Heliograph''.
In 1888,
Ferdinand Hurter
Ferdinand Hurter (15 March 1844 – 12 March 1898) was a Swiss industrial chemist who settled in England. He also carried out research into photography.
Early life
Ferdinand Hurter was born in Schaffhausen, Switzerland, the only son of Tobi ...
and
Vero Charles Driffield
Vero Charles Driffield (7 May 1848 – 14 November 1915) was an English chemical substance, chemical engineer who also became involved in photographic research.
Driffield was educated at Liverpool Collegiate Institution, Liverpool Collegiate an ...
patented a device for estimating the actinic power of sunlight and for computing exposure times and apertures for cameras, based on the
plate speed, time of day, time of year, and latitude. These were
slide rule
A slide rule is a hand-operated mechanical calculator consisting of slidable rulers for conducting mathematical operations such as multiplication, division, exponents, roots, logarithms, and trigonometry. It is one of the simplest analog ...
s, not measuring instruments, and did not produce a graph, but Hurter and Driffield adopted the same name for it.
In 1911, Arthur William Clayden M.A. (Fellow of the Royal Meteorological Society and Principal of the Royal Albert Memorial University College of Exeter) developed a version of an actinograph for meteorologists, to observe and record the change of radiation.
The actinograph: An instrument for observing and recording changes in radiation
(April 1911) Quarterly Journal of the Royal Meteorological Society 37 no. 158, pp, 163–168
See also
*Actinometer
An actinometer is an instrument that can measure the heating power of radiation. Actinometers are used in meteorology to measure solar radiation as pyranometers, pyrheliometers and net radiometers.
An actinometer is a chemical system or physical ...
*Pyranometer
A pyranometer () is a type of actinometer used for measuring solar irradiance on a planar surface and it is designed to measure the solar radiation flux density (W/m2) from the hemisphere above within a wavelength range 0.3 μm to 3 μm.
A typ ...
(a type of actinograph)
*Hurter and Driffield
Ferdinand Hurter (1844–1898) and Vero Charles Driffield (1848–1915) were nineteenth-century photographic scientists who brought quantitative scientific practice to photography through the methods of sensitometry and densitometry.
Among th ...
References
Photography equipment
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