Improvements in Photographic Apparatus.
Year: 1891

page_text: Date of Application, 25th Aug., 1891
Complete Specification Left, 23rd May, 1892-Accepted, 25th June, 1892
Co
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I.
PROVISIONAL SPECIFICATION.
Improvements in Photographic Apparatus.
"ARLES WALKER CLARKE of No. 32 Market Place Devizes in the
y of Wilts Bookseller Stationer and Photographer do hereby declare the
of this invention to be as follows:-
This my invention relates to certain improvements in or relating to photographic
apparatus and consists of a shade for cutting off or screening a part of the light
from certain parts of a view during exposure in the camera such as the sky in a
landscape or windows in the case of an interior.
This screen may be of any suitable material but I prefer to use either celluloid
an absolute
or glass stained or tinted in places but graduated off to
transparency.
For taking a landscape photograph I should generally use a screen in such a
position that it would cover the sky as seen through the ground glass, and should
set it in such a position that the transparent edge of the screen just clears the
horizon in the view (this I should regulate by a graduated scale attached to the
screen and a corresponding scale attached to the ground glass).
I find that by this means I am enabled to obtain a negative of much more
uniform density and to obtain pictures of clouds which without the use of the
screen would not appear at all.
The screen may be used in any convenient position either in front, between or
behind the lenses, but I find it convenient to make the screens to slide in a slot in
the same manner as a Waterhouse diaphragm, but sometimes I use either a circular
screen to revolve, a square screen to let down from the top or to be pushed through
the side, inside the camera, with suitable arrangements for manipulating the same
from the outside, this screen is formed either in different shapes or with tints of
different depths or with different patterns (preferably round its circumference) and
is arranged in such a manner that more or less or either tint or pattern or screen
may be brought into the view as required.
To screen a window in the case of an interior exposure I should select a screen
having one or more suitably stained and graduated spots which I should arrange in
such a position that it would shield or screen off the bright rays as seen through
the ground glass of the camera.
It will be understood that the object of this invention is to reduce the greater
illumination proceeding from certain parts of the subject such as the sky or a
window, leaving the darker portions unscreened.
The device may be either combined with the camera, the lens, or the shutter, or
if desired it may be a separate or independent attachment.
It may sometimes be desirable to use two or more screens for different parts of a
subject.
If desired the screen may consist of a cloud scene made by photographic or by
any other means, and used preferably, inside the camera so that by this arrange-
ment clouds may be included in a negative even when the sky is clear, or any other
device by the same means may be formed on the screen for insertion in the
negative.
Dated this 24th day of August 1891.

page_text: COMPLETE SPECIFICATION.
Improvements in Photographic Apparatus.
I CHARLES WALKER CLARKE of No. 32 Market Place Devizes in the
County of Wilts Bookseller Stationer and Photographer do hereby declare the
nature of this my invention to be as follows:-
This invention relates to certain improvements in or relating to photographic
apparatus and consists of a screen for cutting off or screening a part of the light
proceeding from the sky only during exposure in the camera.
This screen may be of any suitable material such as very thin tinted or semi-
transparent glass celluloid or hardened gelatine but I prefer to use glass which
need not be thicker than the "cover" glasses used for the objects of microscopes,
the upper and lower edges of the screen are either straight or curved and if
necessary graduated off to an absolute transparency.
In taking a landscape photograph I should use the screen in such a position that
it would cover the sky as seen through the ground glass of the camera and should
set it in such a position that the lower edge just cleared or coincided with the
horizon in the view this on account of the tint of the screen being plainly visible
on the ground glass being easily adjusted though if necessary the adjustment may
be made by a graduated scale attached to the screen and a corresponding scale
attached to the ground glass. The screen may however be made to cover the
whole of the view in which case that part only which covers or shields the sky
would be tinted and the remaining part left absolutely transparent, or if the whole
of the screen was tinted a deeper tint would be used for that part which shielded
the sky, in the former case the edge of the tint and in the latter the edge of the
deeper tint may if necessary be graduated off and terminate either in a straight line
or curve this screen may be used and operated in the screen-holder B or held in a
rigid position precisely in the same ways and manners as already (or that will be)
described for the screen which covers only a part of the view. In regard to the
screen which covers the whole of the view it must be distinctly understood that
where the edge of the tinted or more deeply tinted part is not graduated off it
should be used only in conjunction with an apparatus imparting to it a movement
such as is described and illustrated in the accompanying drawings but where it is
used in a rigid position it should be used only with the edge of the tinted or more
deeply tinted part graduated off.
The screen may be used in any convenient position either in front between or
behind the lenses but I prefer to use it in front.
Though only a single screen is used at one time a series could be provided suited
to the most common curves formed by the distant horizon in a landscape, the screen
however may be made of any shape, and though I prefer to make it square and
have only two different patterns on each, it could be made circular, with several
different patterns round its circumference, and be made to revolve so as to bring
them severally into position either before or behind the lens.
The screen may be attached to and worked with any kind of shutter whether
"instantaneous "
66
or time" but I prefer to have it attached to and worked with
the ordinary single "flap" shutter if for no other reason than that the flap when
raised for the exposure protects the lens from extraneous light and is in itself a
most valuable adjunct to the lens when used in the
open air.
The screen A (if of a material not sufficiently rigid framed round three of its
sides) is held by and slides perpendicularly in a grooved carrier B which carrier
slides perpendicularly in a slot C immediately behind the flap D and is attached to
the top of the rod by which the flap is raised by a cord running through a pulley
depending over the carrier (the screen may be drawn into its place and removed by
an adjustable arm or spring or by any other means thought desirable) so that when
the flap is raised and the rod revolved the carrier holding the screen descends
rising again as the flap falls.

page_text: The screen (framed or unframed) fits in the grooved carrier B so that it can be
aised or lowered to suit the line of the horizon and having its upper and lower
edges differently curved it can be placed in the carrier with either edge down in
the position to be used or it may be placed in the carrier with the curves reversed,
by means of a sliding-back E (into which the lens fits) an horizontal adjustment
may be obtained, while by a turn of the complete apparatus on the lens-tube the
screen may be tilted up at either side, and by a telescopic arrangement of the
hoods or tubes attached to the sliding-back E (and into which the lens fits)
the distance of the screen from the lens and consequently the apparent size of
the screen may be varied. By these methods every possible movement is secured,
and the pattern of the particular screen used made capable of being adjusted in an
almost unlimited number of positions in order to its lower edge coinciding with the
line of the horizon.
In the case of material such as celluloid being used for the screens, pieces of a
suitable size to fit the carriers may be carried with the apparatus and cut to suit
particular horizons where the view is taken.
On the raising of the flap D the carrier B holding the screen A slides down the
slot C in which position the particular pattern required can by the various move-
ments before mentioned be adjusted to the line of the horizon.
If desired the working parts of the shutter may be so arranged that the screen
will not descend so as to shield any part of the sky until after the shutter is fully
open, when it will fall to the line of the horizon, giving thus an absolute
preliminary exposure to the whole instead of only a part of the view, the screen
being wholly removed again before the lens begins to be covered by the closing
shutter.
The screen may be so constructed that it may be inserted and used in the
diaphragm slot together with or instead of the stop, either in a fixed position or so
connected with the working parts of a shutter as to fall and rise as the shutter
opens and closes giving similar effects to those obtained by the shutter used in front
of the lens.
The density of a screen may be increased by employing two or more screens
overlapping one another and using them in the same ways and manners as a single
screen.
It will be understood that the object of the movement imparted to the screen by
the working of the shutter is that while the flap is rising and before the screen can
fall so as to completely shield the sky, a short but absolute exposure is made of
the line of the horizon (where the exposure required is generally less than for the
foreground) the same brief exposure of the horizon being again repeated as the
flap falls and the shutter closes. The vignetting effect of this movement in respect
of the horizon and any objects upon it, supplemented by that caused by the
graduated edge of the screen, and the vignetting property possessed by the lens
itself in respect to any substance tolerably close to it will leave in the resulting
negative taken under these conditions no indication of any intervening medium
between the lens and the sky having been used.
The screen may be adapted to and worked together with any shutter having
perpendicular or other movements, but so connected therewith that upon the
raising of the shutter the screen descends by a perpendicular movement to meet
the line of the horizon (of course these movements are reversed in using the
shutter behind the lens) not however before a brief but absolute exposure has been
given to any objects thereon, this brief exposure being repeated as the shutter falls
as before explained, and the best results due to this combined movement are
obtained by the use of such a stop as will allow of a gradual and continuous raising
and lowering or opening and closing of the shutter the whole exposure being
completed in this way in as brief a time as possible this method of making the
exposure (viz. the avoidance of any pause) contributing to the accurate vignetting
of the horizon.
If however it is desired to dispense with a preliminary exposure of the horizon,

page_text: the screen (which should have its lower edge graduated off to an absolute trans-
parency) may be fixed in any perpendicular or slanting position in respect to the
lens or shutter to either of which or to the camera it may be attached or connected
by an adjustable arm, or it may be so arranged within the camera as to be capable
of being raised or lowered, moved horizontally or tilted from the outside, but
though the fixed position without the preliminary exposure movement may be
adopted it is not recommended.
The screen used in a fixed or rigid position may have if circular its edge
graduated off to an absolute transparency and formed into various curves so that
the same screen may be capable of being used in different positions, or the thick-
ness of the material of which a screen may be composed may be varied so as to
present the thinnest possible substance where it meets the horizon.
It will be understood that by the use of a screen suitably tinted (such as with a
yellow orange or green tint) and suitably shaped shielding the sky only in
such a way as not to interfere with a proper exposure of objects on the line of the
horizon, a compensation will at once be obtained for the greater illumination
proceeding from the sky than from the land and in the vast number of landscape
photographs where the outline of the horizon though curved is well defined, the
clouds when present may be retained and by one simultaneous exposure rendered
as correctly and as truthfully as the foreground, while in seascapes especially where
there is an uninterrupted horizon their retention will be reduced to simplicity
itself.
I do not however confine myself to the arrangements and devices before described
as it will be obvious that they may be greatly varied without departing from the
spirit of the invention.
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. The combination with an apparatus for exposing a photographic plate or film
of a semitransparent or tinted screen so arranged that it only covers a part of the
view and is brought into position after the view or a portion of the view has had a
short but complete exposure substantially as described.
2. The combination with an apparatus for exposing a photographic plate or film-
of a semitransparent or tinted screen which only covers a part of the view so
arranged that it can be partially or wholly removed giving a short but complete
exposure to a part or the whole of the screened portion of the view before the
shutter is closed substantially as described.
3. The combination with an apparatus for exposing a photographic plate or film
of a semitransparent or tinted screen which only covers a part of the view so
arranged and operated that a short but complete exposure is given to a part or the
whole of the screened portion of the view both before and after the screen is
brought into operation, substantially as described.
4. The combination with an apparatus for exposing a photographic plate or film
of a semitransparent or tinted screen so arranged that it only covers a part of the
view, and is graduated off to an absolute transparency at one or more of its edges
and so arranged that it reduces the amount of light which reaches a portion of the
photographic plate or film substantially as described.
5. The combination with a photographic lens of a semitransparent or tinted
screen which only covers a part of the view and which is graduated off to an
absolute transparency at one or more of its edges and so constructed that it may be
inserted and used in the diaphragm slot together with or instead of the stop
substantially as described.
6. The combination with a photographic lens of a semitransparent or tinted
screen which only covers a part of the view the form of which is capable of being.
cut or altered to suit the subject intended to be taken on the photographic plate or
film substantially as described.

page_text: 7. The combination with an apparatus for exposing a photographic plate or film
of a frame such as B arranged to hold a semitransparent or tinted screen such as A
and which slides in a slot such as C and is connected with the top of the rod by
which the flap D is worked substantially as and for the purpose described and
illustrated in the accompanying drawings.
8. The combination of a semitransparent or tinted screen such as A with a frame
such as B arranged to be brought into operation by the movement of the shutter D
substantially as described and illustrated in the accompanying drawings.
9. The combination with an apparatus for exposing a photographic plate or film
of a semitransparent or tinted screen which only covers a part of the view and
which is graduated off to an absolute transparency at one or more of its edges and
has one or more of its edges straight or curved and is supported in front or behind
the lens in such a manner that it reduces the light which reaches certain portions
of the photographic plate or film substantially as described.
10. The combination with an apparatus for exposing a photographic plate or
film of two or more semitransparent or tinted screens which will only cover part of
the view and which are graduated off to an absolute transparency at one or more
of their edges and have one or more of their edges formed either straight or curved
and which are so arranged that they obstruct or reduce the light which reaches
certain portions of the sensitive plate or film.
11. The combination of a photographic camera with a semitransparent or tinted
screen which only covers a part of the view and which is graduated off to an
absolute transparency at one or more of its edges (which if desired may be curved)
and which is arranged behind the lens and inside the camera in such a manner that
it screens or reduces the light which reaches certain portions of the photographic
plate or film and that it may be adjusted from the outside and operated either by
the action of the shutter or independently substantially as described.
12. The combination with an apparatus for exposing a photographic plate or
film of a transparent screen having more or less but not the whole of its surface
stained or tinted in such a manner that it obstructs or reduces the light which
reaches the sensitive surface from the lighter part or parts of a view substantially
as and for the purpose described.
13. The combination with an apparatus for exposing a photographic plate or
film of a transparent screen which is stained or tinted more at certain parts than
others in order to reduce or qualify the light which reaches the sensitive surface
substantially as and for the purpose described.
Dated this 21st day of May 1892.