Improvements in the Application of Electric Light for Photographic Purposes.
Year: 1893

page_text: Date of Application, 10th Nov., 1893
Complete Specification Left, 22nd Mar., 1894-Accepted, 28th Apr., 1894
PROVISIONAL SPECIFICATION.
Improvements in the Application of Electric Light for Photographic
Purposes.
I ANDREW GEORGE ADAMSON, of 136 Buchanan Street, Glasgow, Photographic
Artist, do hereby declare the nature of this invention to be as follows:-
This invention relates to Improvements in the Application of Electric Light for
Photographic Purposes. Hitherto the electric light has been used for taking
photographs by means of the arc light, but there are objections to the are light on
account of the variations in brightness and also in the colour of the light. In
order to overcome these objections I propose to use the incandescent light. The
incandescent lamps when used with the ordinary current give too yellow a light for
photographic purposes. I therefore use a stronger current and obtain a light
sufficiently bright for taking photographs. If this strong current were kept
running for any considerable time through the lamps they would last a very short
time, besides the strong light would be injurious to the pupil of the eye of the
person being photographed. I therefore provide a resistance coil through which
the current passes to the lamp, and at the instant of exposing the plate I switch
out the resistance and obtain the bright light for a few seconds, during which the
photograph is being taken. As soon as the exposure of the plate is over, the
resistance is again switched into circuit, and the normal current passes through
the lamp.
The lamps are placed round the inside of a dome-shaped chamber or reflector
which is suspended from a suitable bracket and is so arranged that it can be moved
about to any part of the room and adjusted to any convenient angle.
Dated this 9th day of November 1893.
BOTTOMLEY & LIDDLE,
154, St. Vincent Street, Glasgow, Applicant's Agents.
COMPLETE SPECIFICATION.
Improvements in the Application of Electric Light for Photographic
Purposes.
I, ANDREW GEORGE ADAMSON, of 136 Buchanan Street, Glasgow, Photographic
Artist, do hereby declare the nature of this invention and in what manner the
same is to be performed to be particularly described and ascertained in and by
the following statement :-
This invention relates to Improvements in the Application of Electric Light for
Photographic Purposes. Hitherto the electric light has been used for taking
photographs by means of the arc light, but there are objections to the arc light on
account of its unsteadiness and its variabilities of colour, which cause the actinic
force of the light to be an unknown quantity, and the exposure of the sensitive
plate a matter of guess; also its proneness to hiss and spark, causing the person
being photographed to become nervous.
In order to overcome these objections I propose to use the incandescent light.
The incandescent lamps when used with the ordinary pressure or voltage intended
in their manufacture give too yellow a light for photographic purposes. I
therefore use a stronger current and obtain a light of great actinic force and

page_text: suitability for taking photographs. If this strong current were kept running for
any considerable time through the lamps they would last a very short time, besides
the strong light would be injurious to the eyes of the person being photographed if
continued for any length of time. I therefore provide a graded resistance through
which the current passes to the lamps, and when the exposure of the sensitive plate
is about to be made I switch on the main current with the whole resistance in
circuit. The lamps therefore burn very dimly, and the eyes of the sitter are saved
the shock which would arise by any sudden transition from subdued to very bright
light. The resistance is then slowly switched out of circuit, and at the instant
when it is entirely cut out, the exposure of the plate is made, and I obtain the
bright light for a few seconds, during which the photograph is being taken. As
soon as the exposure of the plate is over the resistance is again switched into
circuit, and the normal current passes through the lamps, but as the current
required to give a sufficiency of light is very great I effect a great economy and at
the same time permit the eyes of the person being photographed to be kept in a
subdued light by suspending in the centre of the reflector hereinafter described a
large single lamp, or lamps, which is or are adjusted to give the same angle of
light as that obtained from the main body of the reflector, and at the same time
give sufficient light to enable the operator to adjust the image on the screen of the
.camera.
In order that my invention may be properly understood and readily carried into
effect I have shown a form of apparatus which I prefer to adopt in the application
of the incandescent light for photographic purposes, of which―
Figure 1 is an elevation.
Figure 2 is a part section and part elevation drawn to an enlarged scale of the
dome-shaped chamber or reflector on which the lamps are carried; and
Figure 3 is a view of the resistance coil.
As will be seen from the drawings the chamber A. is suspended at one end of a
bracket or beam B which is pivoted at C and has a counterweight D at its opposite
end. This bracket or beam B is connected to a carriage E, which runs on rails F,
so that the apparatus can be moved to any part of the studio, or adjusted. The
dome shaped chamber A is pivoted at G, so that it can be adjusted to any suitable
angle. The lamps H are placed round the inside of this chamber A.
With reference to Figure 3, A¹ are the carbon rods; B¹ brass couplings with
binding screws to connect wire to switch-board; C¹ is where current enters; and
D' is where current leaves; E' is a circular plate with rubbing contact; while F¹
is a metal rod with insulated handle for turning off and on.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
The application of the incandescent electric light for photographic purposes
substantially as and for the purposes herein before described.
Dated this 20th day of March 1894.
BOTTOMLEY & LIDDLE,
154, St. Vincent Street, Glasgow, Applicant's Agents.