Thomas Sutton e Robert Macpherson: 1853: panorama di Roma dal Gianicolo
«Photographic Notes. Journal of the
Photographic Society of Scotland and of the Manchester Photographic
Society », il periodico edito a Londra da Thomas Sutton per undici
anni a partire dal 1856, è una fonte di grande interesse per la storia della
Nella nota On
the use of bromine (vol. I, 1856, n. 1, 1 gennaio, p. 10), Sutton riferisce in dettaglio di una fotografia ripresa da lui insieme
a Macpherson nel 1853: un panorama di Roma dal Gianicolo.
È questa una
notizia di notevole interesse finora non valutata nella storiografia di
« On the Use of Bromine
There are certain branches of Photography in
which the use of Bromine in conjunction with Iodine, does not appear to be
sufficiently recognised. I allude more particularly to the Calotype Process on
paper; and the Albumen Process on glass, as practised by certain artists.
If we refer to the early history of the
Daguerreotype process, in which the silver plate was merely submitted to the
fumes of iodine, we find that it possessed but little sensibility; half an hour
being required for a portrait, with a double lens, and a whole morning for a
view in full sunshine with a single lens. At the present day, when a certain
proportion of bromine is introduced with the iodine, the plate becomes
highly sensitive; and a certain proportion of chlorine in addition to
this, increases the sensitiveness still more. Also, if the plate, instead of
being chemically clean, should contain any traces of oil, the sensitiveness
will be heightened still further.
But observe, that in theseexperiments, there
are certain proportions of the haloid elements, which give the greatest
amount of sensitiveness. Too much or too little bromine, or chlorine affect the
These facts have an important bearing upon
other branches of photography in which the same elements are introduced.
Take for instance an albumenized plate,
containing merely iodide of silver. This will be found to possess but little
sensitiveness. I will state an anecdote in connection with this circumstance.
When I was in Rome 3 years ago, I took an
albumen picture in company with Mr. Macpherson. It was a magnificent sunny day.
The view we took was that of the city, from the Janiculum. The sun was at our
back, and the whole scene which included a vast extent of Campagna and the
distant mountains, lay in one blaze of light. (By the bye, this was entirely
wrong; for owing to the absence of shadows, the picture looked flat and tame to
a degree. But we must all learn by experience.)
We exposed to this view, one whole hour, and
on developing the picture, it was not over done. The plate merely contained
iodide of silver. Around each outline of the different objects in the view
there was a sort of light halo, which gave to the print a hard, wiry
Now we have no right to attribute this want
of sensitiveness to any peculiar quality of the Albumen… I believe the Albumen
to be nearly inert in the matter. The most instantaneous picture ever yet taken
was by Mr. Fox Talbot, on an albumenized plate. A Positive print on albumenized
paper, prints quite as quickly as one on plain paper. The want of sensitiveness
was owing to the want of Bromine. Again, in the Calotype process, unless the
weather is very hot, and the paper well sized with some organic matter, it is
necessary to add gallic acid to the sensitive solution, in consequence of the
absence of Bromine. And it sometimes happens, that with any amount of exposure there are certain dark parts
of the view which will not come out; but which can be obtained by
the Daguerreotype, or the Collodion, or the Waxed paper process, in which
bromine is introduced.
All these facts
appear to me to indicate the importance of combining Bromine with Iodine, in
the first preparation, in some certain proportion.
succeeded lately in making a very good Calotype paper, in which I have overcome
the difficulty of introducing the Bromine. This paper requires no gallic acid
to be added to the sensitive solution.