Improvements in Instruments for Calculating Photographic Exposures.
Year: 1894

page_text: Date of Application, 21st Feb., 1894
Complete Specification Left, 20th Nov., 1894-Accepted, 29th Dec., 1894
PROVISIONAL SPECIFICATION.
Improvements in Instruments for Calculating Photographic
Exposures.
I, RICHARD WHITEHORNE SAVAGE of 17 Eldon Place Leeds in the County
of York Architect and Surveyor, do hereby declare the nature of this invention to
be as follows:-
My invention relates to an improved form of instrument for calculating photo-
graphic exposures, made of a compact size and shape for carrying conveniently in
the vest pocket.
In instruments where the scales are placed longitudinally they are of an
excessive length and where the scales are on circular rings their range is limited,
except the diameter of the instrument be increased to an inconvenient size.
To improve upon these I make my instrument, of ivory, bone, celluloid or other
composite substances but preferably of metal, in the form of a pencil case, with a
main tube, hereinafter called the first, of small diameter and of suitable length,
having five other tubes, respectively called the second, third fourth, fifth and sixth
tubes, fitting loosely upon the first tube, one over the other, in the above order, and
each shorter than the one immediately beneath it, and of sufficient diameter to
move easily.
These five (second to sixth inclusive) superimposed tubes, the second of about
half the length of the first tube, are so arranged that they, except the sixth and
outer, have each one end visible & fitted with a narrow milled ring, and the other
end under the tube above; the whole of the covered ends lying together at one
end, called the left, of the first tube.
The sixth and outer tube has its whole length visible, one end with a milled
ring as before and the other secured by suitable means to the left end of the first
tube, leaving the intermediate tubes free to move when actuated by the milled
rings.
Åround the first tube I form a narrow continuous spiral groove and upon the
outer surfaces of the four following tubes are similar spiral grooves or indents
showing as spiral ridges internally, corresponding in pitch to the groove upon the
first tube, each internal ridge fitting into the groove on the tube immediately
beneath it.
Instead of a spiral groove upon the first tube it may have a spiral ridge; then
the grooves and ridges upon the shorter tubes would be reversed to ridge externally
and groove internally.
The movement of the tubes would be the same in either case, the object being to
give the surfaces of each a spiral motion to right or left as the tubes are moved by
the milled rings.
Upon the first and the four following tubes I place, etch, or engrave scales, the
figured divisions following the spiral spaces between the grooves or ridges.
These five scales are well known to, and used by photographers for calculating
the correct exposure with the help of an actinometer for testing the light.
1
By marking or placing the scales spirally round the tubes I am enabled to have
a large number of divisions, giving a great range to each scale without making the
instrument of great length or inconveniently bulky.
But as some of the scales are only of a short length, with few divisions, I do not

page_text: confine myself to placing all of them spirally; one preferably the outer may be
arranged longitudinally, parallel to the axis of the pencil and in this case moving
longitudinally, whilst the remainder would move spirally as before described.
"
The scale on the first tube is for the "exposure," on the second for the "stop
or "diaphragm," on the third for the "speed of plate" on the fourth for the
"subject" and on the fifth for the "actinic intensity of the "light" as found by the
actinometer in the usual way.
Any other order may be adopted for the intermediate scales or a less or greater
number may be used, the working being the same.
Marked upon the outer and ringed ends of the second, third, fourth, fifth and
sixth tubes are pointers each with a word or letter descriptive of and pointing to
the divisions of the scale on the tube next below it.
Each scale is moved by the milled rings, till the several pointers are opposite the
selected numbers on each scale, the number upon the scale on the first tube
indicating the requisite exposure.
In the above movements the result of turning the several tubes causes the scales
to move spirally, one over the other and to the right or left as required. To
prevent the intermediate tubes moving too far on each other to the right and
thereby concealing or covering the marked pointers, I place or work a small pin or
projection on each tube.
Instead of the scales being etched or engraved upon the surfaces of the tubes
they may be more economically, stamped or marked upon flat strips of metal and
then wound in a tubular form, with an open spiral slit left between the edges of
the strip secured & strengthened at one end with a milled ring as before
described.
The first tube would then have upon its surface a deep spiral ridge or thread as
a guide for the slits on the succeeding spiral strips to work on governing their
motion as previously described in the case of the tubes.
"
The position of the pointer marked "light" upon the sixth or outer tube relative
to the position of the numbers on the "exposure" scale on the first tube depends
upon the standard of light selected and the above pointer & scale or their
equivalents, are usually so fixed that the instrument is only capable of being used
with one standard of light.
The sixth and first tubes may be fixed together for one standard of light or
preferably the connection may be made adjustable by slots or notches or other
suitable means, so that their relative positions can be readily altered according to
the particular standard of light adapted.
I arrange the larger and left end of the instrument as an actinometer the first
or inner tube carrying a strip of paper sensitive to and darkening under the action
of light in the usual way.
A movable cap is fitted with a coloured piece of paper, either, all of one tint, or
half of its surface of twice the depth of tint of the other, the former or darker I
call the "full" tint, the latter the "half" tint.
In the centre of the coloured paper is a small opening, preferably circular or
oval, half of its area lying in one tint and half in the other.
The sensitive strip of paper is exposed through this opening, a fresh portion
being drawn out as required in the usual way, the time taken to darken it to the
depth of either tint as selected, being noted.
The "full" tint is used under ordinary circumstances the "half" tint when the
light is feeble to save time. In the latter case the exposure number is doubled.
At the right hand of the instrument & fitting into the first or inner tube, I place
a pencil or pencil tube or combined pen and pencil fitting, either to draw or screw
out in the usual way.
Dated this 20th day of February 1894.

page_text: Improvements in Instruments for Calculating Photographic
Exposures.
I RICHARD WHITEHORNE SAVAGE of 17 Eldon Place Leeds in the County of
York, Architect and Surveyor, 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 :-
My invention relates to an improved form of instrument for calculating photo-
graphic exposures, made of a compact size and shape for carrying conveniently in
the vest pocket. In instruments where the scales are placed longitudinally they
are of an excessive length and where the scales are on circular rings their range is
limited except the diameter of the instrument be increased to an inconvenient size.
To improve upon these I make my instrument of ivory, bone, celluloid or other
composite substances, but preferably of metal, in the form of a pencil case, Figs. 1
and 4, with a maiu tube N, of small diameter, and of suitable length, having five
other tubes, O. Q. R. T. W. Figs. 1 and 4, fitting loosely upon tube N, one over
the other, in the above order, and each shorter than the one immediately beneath
it, and of sufficient diameter to move easily.
These five superimposed tubes, O. Q. R. T. W. Figs. 1 & 4. (tube O about half
the length of tube N) are so arranged that they, except tube W have each one
end visible and fitted with a narrow milled ring, C. C. C. C. Figs. 1 and 4. and
the other end under the tube above; the whole of the covered ends lying together
at one end, A Figs. 1 and 4.
The outer tube W Figs. 1 & 4 has its whole length visible one end formed with
a milled ring F. Figs. 1 and 4, and secured by suitable means to the end of tube N
at A, leaving the intermediate tubes free to move when actuated by the milled
rings C. C. C. C Figs. 1 and 4.
Around tube N I form a narrow continuous spiral groove, and upon the outer
surfaces of the four following tubes, O. Q. R. T are similar spiral grooves or
indents showing as spiral ridges internally, corresponding in pitch to the groove
upon tube N, each internal ridge fitting into the groove on the tube immediately
beneath it.
Instead of a spiral groove upon tube N it may have a spiral ridge, then the
grooves and ridges upon the shorter tubes would be reversed, to ridge externally
and groove internally.
The movement of the tubes would be the same in either case, the object being to
give the surfaces of each, a spiral motion to right or left as the tubes are moved by
the milled rings, C. C. C. C.
Upon the tubes N. O. Q. R. T. 1 place, etch, or engrave scales, the figured
divisions following the spiral spaces between the grooves or ridges.
These five scales are well known and used by photographers for calculating the
correct exposure with the help of an actinometer for testing the light.
By marking or placing the scales spirally round the tubes I am enabled to have
a large number of divisions giving a great range to each scale, without making the
instrument of great length or inconveniently bulky.
But as some of the scales are only of a short length with few divisions I do not
confine myself to placing all of them spirally; one or more may be arranged
longitudinally parallel to the axis of the pencil, and in this case moving longi-
tudinally, whilst the remainder would move spirally as before described.
The scale on the tube N is for the "exposure" on O for the "stop" or
"diaphragm," on Q for the "speed of plate" on R for the "subject" and on T for

page_text: the
actinic
usual way.
intensity of the · light´ as found by the actinometer in the
Any other order may be adopted for the intermediate scales, or a less or greater
number may be used the working being the same.
Marked or formed upon the outer or ringed ends of tubes, O. Q. R. T. W.
Fig. 1. are pointers each with a word or letter, E. D. P. S. L Fig. 1, descriptive
of & pointing to the divisions of the scale on the tube next below it.
Each scale is moved by the milled rings C. C. C. C Figs. 1 and 4. till the several
pointers are opposite the selected numbers on each scale, the number upon the
scale upon tube N indicating the required exposure.
In the above movements the result of turning the several tubes causes the scales
to move spirally one over the other and to the right or left as required. To
prevent the intermediate tubes moving too far on each other to the right and
thereby concealing or covering the marked pointers, I place or work a small pin or
projection on each tube.
Instead of the scales being etched or engraved upon the surfaces of the tubes
they may be more economically stamped or marked upon flat strips of metal and
then wound in a tubular form with an open spiral slit, left between the edges of
the strip, secured and strengthened at one end with a milled ring as before
described.
The tube N would then have upon its surface a deep spiral ridge or thread as a
guide for the slits on the succeeding spiral strips to work on, and governing their
motion as previously described in the case of the tubes.
The position of the pointer marked L, Fig. 1 upon the outer tube W relative to
the position of the numbers on the exposure scale on tube N, depends upon the
standard of light selected and the above pointer and scale or their equivalents, are
usually so fixed that the instrument is only capable of being used with one standard
of light. The tubes W & N may be fixed together for one standard of light, or
preferably the connection may be made adjustable by slots or notches in the
end of tube N or by other suitable means so that their relative positions can be
readily altered according to the particular standard of light or speed numbers,
adopted.
I arrange the larger end of the instrument A Figs. 1 and 4, as an actinometer,
the first or inner tube carrying a strip of paper G. Figs. 1. 2. 3. and 4, sensitive to
and darkening under the action of light in the usual way.
A moveable cap (or the outer end of tube W), is fitted with a coloured piece of
paper H Fig. 4 protected by glass J. Fig. 4; the paper either all of one tint or
half of its surface of twice the depth of tint of the other, the former or darker
I call the "full" tint, V Figs. 2 & 3 the latter the "half" tint, M Fig. 3.
In the centre of the coloured paper is a small opening K. Figs. 2 and 3.
preferably circular or oval half of its area, as in Fig. 3, lying in one tint and half
in the other. The sensitive strip of paper is exposed through this opening, a fresh
portion being drawn out as required in the usual way, the time taken to darken it,
to the depth of either tint, as selected, being noted.
The "full" tint is used under ordinary circumstances, the "half" tint where the
light is feeble to save time. In the latter case the exposure number is doubled.
At the smaller end of the instrument B. Figs. 1 and 4, and fitting into tube N,
I place a pencil or pencil tube or combined pen and pencil fitting, either fixed or to
draw or screw out in the usual way.
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. An improved instrument for calculating photographic exposures, consisting of
the combination of a set of scales, all moving spirally, or part moving spirally and
part longitudinally, an actinometer and a pencil case with pen or pencil or both
substantially as described

page_text: 2. The combination in an instrument for calculating photographic exposures, of
moveable scales, and the means of readily adjusting or altering the relative
positions of one or more scales to the others, so that the instrument can be
used with different "standards of light or "speed" numbers,-substantially-as-
described.
"
Dated this 19th day of November 1894.
RICHARD WHITEHORNE SAVAGE.