AN IMPROVED PHOTOGRAPHIC TESTING PLATE OR ACTINOMETER
Year: 1876

page_text: LETTERS PATENT to William Alexander Brice, of 53, Chancery Lane, in the
County of Middlesex, for the Invention of "AN IMPROVED PHOTOGRAPHIC
TESTING PLATE OR ACTINOMETER
"
ealed the 21st October 1876, and dated the 30th August 1876.
COMPLETE SPECIFICATION filed by the said William Alexander Brice at the
Office of the Commissioners of Patents on the 30th August 1876.
WILLIAM ALEXANDER BRICE, of 53, Chancery Lane, in the County of Middlesex.
"AN IMPROVED PHOTOGRAPHIC TESTING PLATE OR ACTINOMETER.”
The object of my Invention is to furnish to photographers an improved testing
plate that may be readily applied to the camera for the purpose of enabling them
in a very convenient and reliable manner to determine with considerable cei tainty
the quality of the chemicals employed, the quick or slow working of the lens, and to
define whether the presence of "fog," or want of clearness in the picture is attri-
butable to impurities of the chemicals, alkalinity of the bath, diffused light, over
exposure to light, or to other causes.
The Invention consists of a frame with a sliding glass plate to which are applied
fixed pieces of transparent material superposed in layers of one, two, three and more
in regular succession to produce a greater or less obstacle to the passage of the light
In the accompanying Drawing, Figure 1 represents a front view of my improved
photographic testing plate or actinometer, Figure 2 a vertical transverse section on
the line,, Figure 1, and Figure 3 a horizontal section on line c, c, Figure 1
Similar letters of reference indicate corresponding parts.
In the Drawing, A represents a wooden frame adapted to any size of camera and
attached by means of hinges and hooks or screws in such a manner that it may be
placed into position for use or moved out of the way to allow the taking of the
photographs in the usual manner Into grooves of the wooden frame A is let
loosely so as to be adjustable to different heights a glass plate B that is provided on
one face or side with a series of fixed plates or sheets C of transparent material,
which are arranged in such a manner that by the superposition of two, three, or
more thicknesses a greater or less resistance is produced to the passage of the light.
The transparent sheets may be employed in any suitable manner in longitudinal or
[Price 4d1

page_text: lateral direction, and preferably so that the centre part of the glass plate is left free
while the adjoining parts are covered with one layer of transparent material, the
next adjoining sections of the plates covered by two layers or thicknesses, and so on
with three or more layers to the ends or sides of the plate
The testing plate formed by the layers of transparent material on the sliding glass
plate is set up between the lens and the sensitized plate, and the picture is then
taken in the usual manner The result is a picture which produces the light, shade,
or shadow of the object to be photographed with the chemicals and lens, and with
light of more or less the samo actinic quality intended to be used for the picture to
be taken. When the picture is developed on the plate we find that the whole picture
is visible, but that it is divided into sections of unequal intensity, being more or less
distinct according as the light had to pass through one or more layers The absence
of fog at the place where the light had to pass through several layers or sheets of trans-
parent material indicates that the chemicals are pure, that there is no diffused light,
and that the nitrate bath is of proper acidity. If at that section details of the picture
are clearly developed we can concludo that the exposure has been sufficient with the
lens, light, and chemicals used The second section of the testing plate where the
light had to pass through a less number of layers gives more or less the same infor-
mation, but indicates more clearly whether the exposure has been adapted to the
existing conditions or not The next section indicates if properly developed what
time, chemicals, &c are to be used for the picture to be taken, while the middle or
uncovered section indicates by the evident over exposure that the lens is good and
rapid in action, that the chemicals are in good condition, and that the light is suffi-
cient in actinic power to produce good pictures with rapid exposure. The different
sections of the testing plate admit thus in a quick and reliable manner a con-
clusion as to the quality of the chemicals, lens, and light, and furnishes thereby
to the photographer a cheap and simple device of adapting himself quickly and
successfully to circumstances, and produce good pictures without losing the best
hours of the light by a failure of the chemical apparatus or erroneous longth of
exposure.
Having described the nature of the said Invention and the manner of performing
the same, I declare that what I claim as new and desire to secure by Letters Patent
is a photographic testing plate or actinometer made of a sliding glass plate adjust-
able in a suitable fiame and divided by superposed sheets or layers of transparent
material into sections forming greater or less resistance to the passage of the light,
substantially in the manner and for the purpose set forth.
In witness whereof, I, the said William Alexander Brice, have hereunto set
my hand and seal, this Thirtieth day of August, in the year of our Lord
One thousand eight hundred and seventy-six.
TET