Improvements in Actinometers and Apparatus for Calculating Photographic Exposures.
Year: 1898

page_text: Date of Application, 26th May, 1898-Accepted, 8th Oct., 1898
COMPLETE SPECIFICATION.
Improvements in Actinometers and Apparatus for Calculating
Photographic Exposures.
I, JOHN ALBERT CHEAPE, of the City of Charlottesville, in the County of Albe-
marle, and State of Virginia, United States of America, Gentleman, do hereby
declare the nature of this invention and in what manner the same is to be per-
formed, to be particularly described and ascertained in and by the following
statement;-
My object is to provide an actinometer wherein one can determine the strength
of the actinic light in two ways, first, by the slightest printing of a stencil so that
any slow or fast sensitized photographic paper which prints out without develop-
ment may be used, and secondly, by the printing of a paper especially prepared
for the purpose, to a certain given tint.
In the accompanying drawings,
Figure 1 is a perspective view,
Figure 2 is a similar view with the ends reversed and the exposure disc opened,
Figure 3 is a bottom plan,
Figure 4 is a longitudinal section,
Eigure 5 is a section on line 5-5 of Figure 4, and
Figures 6, 7 and 8 are detail views.
The body a, comprises a four sided tube, preferably pocket size. The color
paper or sensitized paper b, is cut in long strips and stored within this tube.
The end 6, of the strip b, extends out of the back end of the tube through a trans-
verse slot c, thence under a stencil plate 7, having a stencil d¹, in the bottom
of the exposure box f. The extended end 6¹, of the sensitized paper is drawn
over the face of a hinged paper carrier g, which serves as a back for the stencil
and this plate is held in closed adjustment against the stencil plate by spring
clasps h, which embrace the sides of the tube. This stencil plate d, forms the
bottom side of the tube. The free ends of the paper carrier g, is provided with a
paper clasp i, and clamping screw j, for holding the extended end b¹, of the sen-
sitized paper down tightly against the upper face of the plate g.
In the present
instance, the letter "E" forms the stencil in the bottom of the exposure box f.
This exposure box is preferably in the form of a perfect cube.
As a means for reducing and regulating the power of the light which enters
the exposure box f, a reflector is attached and consists of a triangular shaped
member hinged at k¹, to be thrown open to receive the light and to be closed to
cut off light. In Figure 4 the arrows indicate the direction of the entering light
as it passes into the exposure box f. This reflector k, can be swung back on the
hinge, far enough to have no effect whatever on the light which enters the
exposure box f, or it can be adjusted to stand at intermediate points within the
arc of a circle, in order to regulate the entrance of the light to the finest possible
point.
In connection with the exposure box I provide two other instrumentalities for
still further regulating the light and they consist of an adjustable slide 1,
Figure 2 and a bellows m, Figure 8. The slide 1, is provided with a series of
rectangular openings 7, technically called "stops." This slide is adapted to be

page_text: slid longitudinally between the guides ", and can be moved backward to bring
any one of the openings 1, over the top of the exposure box f, to reduce the size
of the space through which the light enters. For instance, if the first stop
be moved over the top of the exposure box, the force of the light will be reduced
one-half and the stencil will require double the time. The second stop will
require four times the amount of exposure and time to print and so on.
It is to be understood that each succeeding opening admits just half the amount of
light of the next larger, and consequently with its use, it requires just double the
length of time to print through the stencil. By the use of these openings or
stops the time of the exposure can be calculated with greater accuracy. For
instance, if it takes only three seconds to print with the light passing through
the largest opening, it will take six seconds through the next and twelve through
the next and twenty-four through the fourth. Three seconds and even six are
so short that it is difficult to time and test them, therefore it is best to admit
much less light at a time by means of the slide, or its equivalent hereinafter
described.
"
This bellows
It may sometimes be found preferable to employ a bellows m.
will fold into the exposure box f, or can be pulled out as shown in dotted lines.
The top m, of the bellows is provided with a central opening ml, and a
reflector m. By the use of these regulating devices the exact amount of exposure
required can readily be ascertained.
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The four flat sides A, B, C and D) are provided with registering indicia whereby
the amount of exposure necessary for the plate is determined. The side A, bears
a line of numbers from 1 to 10 inclusive denoting the rapidity of the plate. The
side B, is provided with a slide a¹, containing subject matter indicia such as
heavy foreground," group," building 100 ft." etc. The side C, is provided with
a slide bearing two parallel lines of figures. The upper line commencing at the
rear end of the tube denotes the number of seconds from 1-4 to 640 in which the
paper colours and the lower line commencing at the forward end of the tubes gives
the number of lense stops from 2 to 256. The side 1), bears a line of numbers
from the fraction 128 at the front end to 24 at the rear, representing the right
length of time to expose your plate. a", represents a stopper which fits within
the front end of the tube and closes it.
The second method of determining the strength of the actinic light is by cut-
ting the circular hole r, in the paper carrier g, and covering half the hole with
tinted paper y. The prepared paper goes in the instrument the same way as
before, but with the sensitized side reversed.
The operation is as follows:
Assuming that the rapidity of the plate is 10, the slide a¹, on side B, should be
pushed to bring the arrow thereon opposite number 10 on side A, as seen in
Figure 1. Now if it has taken sixty seconds to color the paper under the
stencil "E," the operator should push the sliding scale on the side C, until the
numeral 60 comes opposite the description of the kind of picture he desires to
take. Upon turning the tube over to the succeeding side 1), the scale thereon
will indicate the right exposure to give your plate opposite any stop which you
may be using.
When the reflector k, is thrown all the way back, as represented in dotted lines
in Figure 4, more light will be admitted and the stencil will print much more
quickly than when the reflector k, is swung over the exposure box, as shown in
Figures 1 and 4.
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:-
1. In an actinometer, a stencil, in combination with a paper holder secured to
open and close behind the stencil, substantially as described.
2. In an actinometer, an exposure box provided with a stencil plate, in com-

page_text: bination with a hinged paper holder adapted to open and close against the stencil
plate, substantially as described.
3. In an actinometer, an exposure box in combination with a paper holder
arranged to swing toward and away from the box, substantially as described.
4. In an actinometer, an exposure box provided with a stencil, in combination
with a hinged paper holder provided with a paper clasping device for holding
the paper down on the holder, substantially as described.
5. In an actinometer, an exposure box provided with means for regulating the
quantity of the light admitted thereto, in combination with a stencil, and a paper
holder movable toward and away from the stencil, substantially as described.
6. In an actinometer, an exposure box provided with a reflector, in combination
with a stencil, and a paper holder movable toward and away from the stencil,
substantially as described.
7. In an actinometer, an exposure box provided with a bellows, in combination
with a stencil device, substantially as described.
8. In an actinometer, an elongated body-portion having an exposure box at one
end, a stencil device, and a slide on the body-portion provided with graduated
stops arranged to be passed over the open end of the box to graduate the light,
substantially as described.
9. In an actinometer, a tubular body-portion provided with slides bearing
registering indicia, in combination with an exposure box, a stencil and a hinged
paper holder arranged to open and close.
10. In an actinometer, an elongated tubular body-portion provided with longi-
tudinally moving shues bearing registering indicia, in combination with an
exposure box and a stencil device, substantially as described.
11. In an aclinometer, the combination with a rectangular tube arranged and
adapted to contain strips of sensitized paper, of a stencil plate at one end of the
tube, said tube being provided with an opening through which the paper is
extended to a point beneath the stencil and a holder on which said extended end is
held to the action of the stencil, and means for clasping the paper on the holder,
substantially as described.
12. In an actinometer, a cubic exposure box provided with a stencil, in com-
bination with a paper holder, one being adapted to open away from the other.
13. In an actinometer, a stencil, in combination with a paper holder, one being
arranged to open away from the other, substantially as described.
14. In an actinometer, an exposure box provided with a bellows and stops, in
combination with a stencil, substantially as described.
15. An actinometer having a paper carrier with a hole therein partly covered
with tinted paper.
Datod this 13th day of May 1898
JOHN ALBERT CHEAPE.
W. Lloyd Wise,
46, Lincoln's Inn Fields, London, W.C., Agent for the Applicant.