34 
FRIDAY, DECEMBER 6TH, 1907. 
Colour “Photography, | 
Me. OTTO PFENNINGER. 
A THIRD lecture was given by Mr. Otto Pfenninger on Colour 
Photography in general and the application of his invented 
One-Exposure-Camera for Colour Photography in particular. 
When opening his lecture he said that colour photography 
could easily be classified into four groups. 
Group z.—Heliography by prismatic interference. Zanker 
and Wiener gave the first ideas of this process, and Professor 
Lippmann in Paris brought the process to a practical issue, which 
is, however, not applicable to publication through the press or 
printing on paper, and can only be used in special viewing 
instruments. 
Group 2.—The additive method of colour photography is 
best known in one of its applications, the chromoscope. This 
instrument was first theoretically suggested by Ducos du Hauron 
(France), in 1869, and then 23 years after its first publication 
it was introduced in a practical form and commercially exploited 
by Ives, of Philadelphia. The chromoscope is a viewing instru- 
ment, and up to now it was impossible to use the instrument for 
the subtractive method, because three negatives of same size 
could not be produced. The ordinary chromoscope is defective, 
in so far that the refractions caused by the glass reflectors are not 
compensated. The defect is of no account however if the photo- 
graphs are taken as well as shown in the same instrument. 
Group 3.—We have colour photography by the coloured lines 
or screen-lpate systems, which was also indicated by Ducos du 
Hauron as far back as 1869, but no results were shown. Professor 
Jolly, of Dublin, elaborated the system and showed some results, 
and he proved the correctness of the theoretical suggestions of 
Ducos du Hauron. Others followed on the same lines, and 
lately Warner-Powrie, of U.S., showed some wonderful results ; 
the colours are very bright and less heavy than in the Lumiére 
autochrome. The orange, green, and violet lines which form the 
screen in Warner-Powrie’s photos are very fine, but not so fine 
that the eye does not detect them in the transparency. ‘There 
are already a great number of new patents announced, which 
claim to do better, but the main idea of all of them is, to form a layer 
of three colours in line, or mosaic or irregular dots (like Lumiere’s 
autochrome), side by side on a plate and then to cover the layer 
