Camera Work: A Photographic Quarterly (1908 (Heft 22))

market in Europe. But I think the Premo Daylight Developing machine,
which is made for ordinary plates, is really better than any other machine for
the Autochromes.
The plate is put into a daylight developing tray under cover of a
changing bag, the developer poured in, and at the end of the two and a half
minutes poured off and clean water poured in—or water with a few drops of
sulphuric acid. The plate is then taken out of the tray and put in the
permanganate bath—and so on.
When it comes to the question of exposure we are really up against the
real difficulty. Many are the "systems" that have been worked out, and
their efficiency is all of the same order—nil. The mechanical solution of
the problem is still to be found. The best system I can recommend is the
development of your sixth sense—exposure.
The makers of the plate give one a good guide to start with, one second
at F.8 in full sunlight on a summer noon. This exposure naturally in-
creases with the time of day and year. On a clear, sunny day in the autumn,
I found two and three seconds the equivalent. The Wynne meter is also
very useful as a guide—in the open air. Indoors it is useless. In the summer
time the sensitometer number is about F.11. For twilight exposure I found
that the time required to tint the paper was the correct time of exposure.
Indoors the question becomes still more complicated. With bright sunlight
outside, a portrait near a window, with shadows lighted up by a reflector,
is fully exposed in about one and a half minutes at F.8.The best guide I
find is to give forty times the exposure one would give on, say, kodak film in
summer—in the autumn and winter, from sixty to eighty times as much.
The plate gets its maximum advantage of rapidity in the brightest light,
and its sensitiveness decreases altogether out of scale and proportion to the
ordinary plate in dull light. In the use of stops this becomes very evident,
for the ratio of exposure with the diminishing of the aperture is sometimes
double the ratio we are accustomed to give with ordinary plates. But, of
even greater importance than this is the influence that the quantity of light
has on the color rendering.
It is strange how little people seem to realize that colors change, and
change drastically, according to the intensity of the light. No less an
authority than Mr. Braun, the celebrated photographer of paintings, has
been quoted as saying that the light on the picture that is to be copied has
no influence on the result. If one has not the powers of observation, a
reference to any scientific work on color would prove the falsity of such a
statement.
Some colors are actually changed by varying the intensity of light, for
instance, bright orange seen in a very weak light assumes a brownish tone,
yellow takes on a decided olive greenish cast, and vermilion loses its orange
tone, and looks a purer red. In fact the whole tendency is towards blue;
which tendency is then further exaggerated on the Autochrome plate. A por-
trait photographed indoors on a dull, gray day has a cold, bluish tone pre-
dominating; outdoors the result is sometimes so blue that one imagines the