HF The History of Photography 600pág

94 The invention of photography
Deutsches Museum, Munich, and first published by the authors in 195920 states :
'Photogr. Versuche von mir mit Steinheil, 1839'. Their process, though very similar
to Talbot's, was apparently worked out independently, although Talbot's second
communication to the Royal Society of 21 February giving his methods must have
been available in Munich by March.
Steinheil was responsible for the construction of the camera, whilst Ko bell attended
to the chemical side. English drawing paper was sensitized several times with silver
chloride solution, and on it engravings could be copied in the sun by superposition
in about five minutes. As regards camera pictures they found-like Talbot-that the
paper was more sensitive when moist, and in order to keep it flat in the camera it
was placed between two sheets of mica. We do not learn the exposure time beyond
Ko bell's general statement, 'If these [the pictures] are not to be too small, they need
an exposure of several hours, according to the intensity of the sunlight.' Judging from
this the three 2 in.-square pictures submitted as specimens cannot have been taken
in less than half an hour or even an hour. In fact they were exposed until a visible
negative image appeared, which means that the process was similar to Talbot's,
Gerber's, Reade's, and Bayard's first process. Fixing was done with either caustic
ammonia, in which case the colour produced was 'a beautiful warm dark brown', or
preferably potassium hyposulphite which imparted a deep violet or even greyishblack
tone.
The negatives were apparently too opaque to print from, for Kobell mentions that
in order to get the light and shade in the right place they had to be re-photographed.
He considered, however, the second pictures (i.e. positives) less good, lacking in
contrast, and the four photographs still preserved at the Deutsches Museum in
Munich are negatives.
The cylindrical camera designed by Steinheil for the experiments foreshadowed
in form Voigtlander's and Thomas Davidson's metal cameras constructed for the
daguerreotype process, though it was made of cardboard. The tube was 3 in. in
diameter and 5 in. long, and provided with diaphragms. The lens was achromatic,
but to judge from the three views-all of buildings in Munich-submitted as specimens
with their report to the Academy, Steinheil's lens was surprisingly poor, for
the sharpness falls off rapidly from the centre. Nevertheless he remarks, 'The precision
far surpasses even the most accomplished [artist's] brush, and is limited only by the
structure of the paper when seen through a magnifying glass.'
Steinheil observed that not all subjects are equally suitable for photography. 'Trees,
lawns, and anything else green have too weak an effect in proportion to the other
colours to give clear pictures ; on the other hand, all well-illuminated buildings,
groups of rocks, etc., give an excellent image, very true to life, so that they can serve
the artist as studies.'
On 28 July Kobell at the Queen's command demonstrated photography at the
royal summer palace of N ymphenburg, and it was presumably on that occasion that
he took the ri-in. view of one wing of the palace. About a fortnight later Kobell
and Steinheil exhibited two small 'light drawings' of the Glypthothek amongst paintings
at the Munich Art Society. The Vossische Zeitung, Berlin, reviewing the exhibition
on 19 August, remarked : 'They have the appearance of Chinese ink drawings,
and are interesting for their novelty and the faithfulness of their representation. These
drawings are still rather imperfect, however, and do not yet satisfy their makers, who
lavished considerable trouble on them, whereas the incomparable method of
Daguerre is admirable in its perfection and is bound to triumph in its practical
application over all its competitors.'21