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John Adolphus Flemer.

An elementary treatise on phototopographic methods and instruments, including a concise review of executed phototopographic surveys and of publicatins on this subject online

. (page 30 of 33)
Online LibraryJohn Adolphus FlemerAn elementary treatise on phototopographic methods and instruments, including a concise review of executed phototopographic surveys and of publicatins on this subject → online text (page 30 of 33)
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paper is not as sensitive as most of the modern " printing-out "
papers. It is coated with albumen and sensitized with a solu-
tion of nitrate of silver.

Shortly before placing this paper in the printing-frame it
should be fumigated with ammonia vapors, thus increasing the
brilliancy of the prints and the sensitiveness of the paper as well
as reducing the time required for the actual printing and facili-
tating the subsequent process of toning by reducing any ten-
dency toward " blistering " (separation of the sensitized film
from the paper).

The fuming should be done only for immediate use of the
paper, as it impairs the keeping qualities of the sensitized coat-
ing before fixing. Fuming is best done in a wooden box about
six inches or more deep and having a wooden grating supported
about three inches above the bottom of the box. A saucer con-
taining some " stronger water of ammonia " is placed on the
bottom of the box, the grating is placed in position with the albu-
menized paper laid flat upon it, and the box is now closed, expos-
ing the paper for fifteen to thirty minutes to the ammonia vapor.
This operation should be conducted under exclusion of light, and



PHOTOGRAPHIC PRINTING. 379

it is recommended to remove the paper from the box at least five
minutes before it is placed in the printing-frame.

As most prints have an unpleasant reddish tint when they
leave the printing-frame they are generally subjected to the
toning process, which converts the reddish tint into a warm
sepia, a brown or a dark-purple tint, approaching a black color,
according to the formula used for preparing the toning- bath
and dependent on the length of time they were exposed in the
printing-frame.

A. Toning Photographic Prints.

Papers requiring development of the latent image, .of course
need no special toning-bath, their pictures appearing under the
action of the developer in soft and warm effects, either in black
and gray or in black and brown tones.

There are many formulas available and many preparations
in the market, both for making separate toning-solutions and
" combined toning-baths," which tone and fix the print at one
immersion. Nearly every brand of printing-out paper is fur-
nished with special directions and formulas for toning, fixing,
and hardening.

All toning-solutions contain besides gold (or platinum) an
alkali (bichromate of soda, borax, carbonate of soda, etc.) to
retard the action of the bath. The more gold the print may
be made to take up, the more the gold deposit will partake of a
ruby color and the more permanent becomes the picture. The
final tone of. the picture is conditioned by both the character
and the quantity of the alkali used to neutralize the acidity of
the gold solution, some alkalies (acetate of soda) giving a brown
to purplish tone, while others (carbonate of soda) produce
tones closely approaching a soft black in the deeper shadows
of the picture. For producing good brown to black tones the
following plain gold "separate toning-bath" may be prepared:

Dissolve 1.3 grammes or 20 grains chloride of gold in 570



380 PHOTOTOPOGRAPHIC METHODS AND INSTRUMENTS.

c.c. or 20 ounces distilled water and label the bottle " Gold
solution."

As this solution contains one grain of gold per ounce of liquid
one may substitute one ounce of the solution in all formulas for
toning-baths for every grain of gold given in the formula.

Next dissolve one ounce each of acetate of soda and car-
bonate of soda in twenty ounces distilled water, shake the mix-
ture well and filter into a bottle.

To prepare the toning-bath one ounce (30 c.c.) of the " gold
solution " is added to forty-eight ounces (1440 c.c.) distilled
water and this solution is neutralized by gradually adding of
the acetate and carbonate of soda solution till litmus paper no
longer changes color when dipped into this mixture. When
cold tones are desired in the picture just enough of the alkaline
solution should be added that red litmus paper turns blue when
dipped into the liquid. An excess of alkali, however, has a ten-
dency to make the prints appear more toned than they really
are, and such prints undergo a decided bleaching in their sub-
sequent immersion in the fixing-bath.

Ten ounces of this toning mixture will suffice to tone about
eight 5X8 prints. To tone more, either a larger quantity may
be made up at once or more of the gold and alkali solutions
may be added to the old bath. The latter method has the advan-
tage that this toning solution may be used at once, whereas the
freshly prepared bath should be made up about twenty-four
hours before it is really wanted, the freshly prepared solution
working less uniform than an older one.

Should this bath tone unevenly or should the prints come
out streaky, it is advised to make the bath slightly alkaline and
diluted with water. The desired tone should be produced in
six to ten minutes.

The temperature of this bath should be kept rather low,
not to exceed 60 F.

The toning process proper is conducted as follows:

After the final washing of the prints in running water suffi-



PHOTOGRAPHIC PRINTING. 381

ciently long to remove all free silver, or in five or six changes
of water, they are transferred, one at a time and face down-
ward, to the toning-bath. The tray meanwhile should be gently
rocked and the prints kept in motion by transferring the lower
ones to the top singly, keeping this process up to maintain a
layer of liquid between the prints and to remove at the same
time any air-bubbles adhering to the film surface, thus assuring
an even toning for all.

Prints first begin to tone on their surface, and if not toned
sufficiently deep, they will turn a reddish brown later in the
fixing- bath. If the original red color appears to have disappeared,
on examining the print through transmitted light, toning may
be stopped.

Prints cannot be toned dark if the printing was not carried
sufficiently far, and it should always be remembered that the
original tone of the print will somewhat fade in the toning- and
fixing-baths. Soon after immersion in the toning-bath, of which
the composition has been given, the prints will change color to
a dark brown, then to purple, and finally to a soft black. As
soon as the prints may have been toned to the desired shade
they are to be removed to clear running water, where they may
remain until enough are ready for the fixing-bath.

If no running water be available the toned prints should
first be placed for about one minute in a saline bath of one
ounce of chloride of sodium (common salt) to sixteen ounces
of water (to stop continued action of toning), to be followed
by a thorough washing in several changes of water before remov-
ing the prints to .the fixing-bath.

B* Fixing Photographic Prints.

After the washing following the saline bath the prints are
immersed for fifteen to twenty minutes in the fixing-bath, keep-
ing the prints in motion, the same as described for the toning
process. A good plain fixing-bath may be made up as follows:



382 PHOTOTOPOGRAPHIC METHODS AND INSTRUMENTS.

Metric Weight. Apothecaries' Weight.

1 80 grammes Hyposulphite of soda 6 oz.

75 grammes Alum (powdered crystals) 2.5 oz.

ii grammes Sulphite of soda (powered crystals). 3 drachms

2000 c.c Distilled water 70 oz.

When all these ingredients have been dissolved, add to the
solution 25 grammes (6 drachms) borax, dissolved in 306 c.c.
(TO oz.) hot water.

This fixing-bath keeps indefinitely and may be made up
in large quantity. It should be prepared fully a day before use.

Directly after fixing, the picture should be washed, for one
hour in clear running water or in ten to fifteen changes of water,
at intervals of fifteen minutes, using a large tray or tank and
keeping the prints separated so the water may have full access
to the film and leach out all unconverted salts. If there is a ten-
dency toward blistering the first change of water may be made
saline.

To make prints flexible and to rob them of a tendency to
roll up it is recommended to immerse them in the following
solution for a minute or two after removal from the final wash-
ing:

Metric Weight. Apothecaries' Weight.

90 c.c Glycerine 3 oz.

120 c.c Alcohol 4 oz.

30 c.c Distilled water i oz.

It is advisable to drain the print well, by drawing its back
over the edge of the tray, to remove as much of the surplus liquid
as possible, before placing the print between blotters to dry
under a light pressure.

C. Formulas for Plain Toning-baths.

For producing deep-purple or bluish-black tones in the final
picture the following plain toning-bath is recommended:

Metric Weight. Apothecaries' Weight.

65 milligrammes. . . Pure chloride of gold i grain

5 grammes Sulphocyanide of ammonia 80 grains

315 c.c Distilled water 11 oz.



PHOTOGRAPHIC PRINTING. 383

For toning gelatine or collodion prints with platinum in
place of gold, the following bath may be given:

Metric Weight. Apothecaries' Weight.

65 milligrammes. . . Chloroplatinite of potassium i grain

0.5 gramme Chloride of sodium (salt) 8 grains

0.5 gramme Citric acid 8 grains

115 c.c ... Distilled water 4 oz.



D. Combined Toning- and Fixing-baths.

When a " combined toning- and fixing-bath " is used, the
prints, after removal from the printing-frame, require no pre-
vious washing before immersion.

A one-solution toning- and fixing-bath may be made up as
follows :

Metric Weight. Apothecaries' Weight. \

65 milligrammes. . . Pure chloride of gold i grain

145 c.c Distilled water 5 oz.

30 grammes Hyposulphite of soda i oz.

4 grammes Sulphocyanide of ammonium. ... i drachm

i gramme Acetate of lead 15 grains

i gramme Nitrate of lead 15 grains

This solution should be well shaken before use, and it is best
prepared a day before wanted.

The following two-solution combined bath keeps better (in
separate bottles) than the one-solution bath:

A.

Metric Weight. Apothecaries' Weight.

30 grammes Hyposulphite of soda i oz.

24 grammes Alum (powdered crystals) 6 drachms

8 grammes Sugar (granulated) 2 drachms

300 c.c Distilled water (cold) 10 oz.

After these chemicals have all been dissolved in the cold water,
15 grammes (4 drachms) borax dissolved in 60 c.c. (2 oz.) hot
water are added and the mixture is well shaken. After allow-



384 PHOTOTOPOGRAPHIC METHODS AND INSTRUMENTS.

ing it to stand for twelve hours the clear liquid may be siphoned
into a bottle marked " Solution A" or " Fixing- solution."

The stock solution for toning is made by dissolving chloride
of gold and sugar of lead in water.

B.

Metric Weight. Apothecaries' Weight.

65 milligrammes. . . . Pure chloride of gold i grain

0.5 gramme Acetate of lead 8 grains

30 c .c Distilled water i oz.

This " gold solution " should be well shaken, but not filtered,
before use.

For the " combined toning- and fixing-bath " mix in the pro-
portion of one part " gold solution " (sol. B) to eight parts " fixing-
solution " (solution A).

Half an ounce of stock solution B (" gold solution ") mixed
with four ounces of stock solution A (" fixing-solution ") will
tone about one dozen 5X8 prints.

The double salt " chloride of gold and sodium," which is
a mixture of chloride of gold and chloride of sodium, can be
more easily handled than the pure chloride of gold in making
the toning-solution, since it contains no free acid. If this crys-
tallizable double salt be used in place of the pure chloride of
gold in preparing the " gold solution " of a toning-bath, double
the quantity will be required of the amount given for the pure
chloride of gold in the preceding formulas.

After the desired tone has been attained for the prints in
the combined bath they should be removed to a saline solution
(i teaspoonful of salt to sixteen ounces water) and immersed
five minutes, after which they are washed in ten to twelve changes
of water at intervals of fifteen minutes.

To insure thorough fixing the prints may be immersed for
ten minutes in the fixing-bath previously given, or in the follow-
ing one, immediately after the first change of water following
the saline bath.



PHOTOGRAPHIC PRINTING. 385

Metric Weight. Apothecaries' Weight.

240 grammes Hyposulphite of soda 8 oz.

30 grammes Sulphite of soda (granulated, dry) . . i oz.

3.5 c.c Sulphuric acid i drachm

960 c.c Distilled water 32 oz.



After removal from this bath the prints should be thoroughly
washed in clear running water for at least one hour or in ten
to fifteen changes of water as previously noted. If the prints
be now immersed in the following bath for five minutes any
remaining trace of " hypo " will be removed and the film will
become hard when dried:



Metric Weight. Apothecaries Weight.

960 c.c Distilled water 32 oz.

30 grammes Powdered alum i oz.

30 grammes Powdered chloride of sodium (salt) . i oz.



After removal from this " hardener and short stop " the
prints are again washed and dried.

Combined baths should be used but once and they should be
kept at a rather low temperature, not much over 50 F.; if the
temperature is allowed to rise much above this the prints will
become stained yellow and the darker tones will be tinged with a*
greenish tint. Prints should not be retained in the water over
two hours. All trays should be kept scrupulously clean and
not interchanged. Whenever prints come out " splotchy " it is
recommended to clean the trays, swabbing them out with diluted
sulphuric acid.

Those who prefer to " cut " their own gold for the " toning-
solution " can make up a stock solution of the " gold solution B "
in the above combined bath as follows:



Metric Weight. Apothecaries' Weight.

156 centigrammes . . Pure metallic gold 24 grains

3.5 c.c Nitric acid i drachm

10.5 c.c Muriatic acid 3 drachms



386 PHOTOTOPOGRAPHIC METHODS AND INSTRUMENTS.

After the gold has been fully dissolved, add 1440 c.c. (48
ounces) distilled water and then add enough bicarbonate of soda
to leave the solution slightly acid, just enough to turn blue litmus
paper red. After shaking well filter into a bottle, add 25 grammes
(384 grains) acetate of lead, and label this stock solution " Gold
solution," or " Solution B " of the combined bath.



CHAPTER XII.

CONCLUSION AND REMARKS ON THE PRECISION OF THE
"POLAR-ICONOMETRIC" METHOD AND GENERAL RE-
MARKS ON TELEPHOTOGRAPHY.



I. General Remarks on Phototopography.

THE main disadvantage in connection with phototopography,
resting principally in the great consumption of time in the pro-
duction of the maps in the office, promises soon to be overcome
through the perfections that are being made in the stereoscopic
methods and instruments. The plotting of from fifteen to thirty
control points, by means of the " polar- iconometric " method
(by the intersections of at least three radials or horizontal direc-
tions for each control point), including the plotting (or the " ori-
entation ") of the necessary picture traces, together with the
verifi cation of the focal lengths of the photographs, may be regarded
as a good day's work.

The main advantage in phototopography, on the other hand,
rests in the rapidity with which the field work may be done.
The phototopographer, spending most of his time in traversing
the country, stopping only long enough at the stations to photo-
graph the panorama, to make sketches, and to observe a few
sets of angles with the transit, can in a few good days cover a
larger territory than is possible with any other surveying .method.

A phototopographic party is essentially an economic, one,
inasmuch as it comprises but one topographer, assisted by as
many packers or hands as may be needed to transport the party
outfit ever the region that is to be surveyed. The time-con-

387



388 PHOTOTOPOGRAFHIC METHODS AND INSTRUMENTS.

suming part of the work (the iconometric plotting) is independent
of weather conditions and may be accomplished at any time
by one or two iconometric draughtsmen in the office.

The ready identification of points on the photographs is a
matter of practice and will be found far less difficult than would
appear at a first attempt. All apparent difficulties in this respect
may soon be overcome by a comparative study of several pic-
tures held side by side, and also by making use .of the numerous
tests and constuctions that are available for this purpose, the
most important of which having been given under Prof. G. Hauck's
method. We have also seen that this difficulty disappears alto-
gether when applying the stereophotographic methods.

To economize in time, the general progress of the field work
should, as far as possible, be regulated by the weather and cli-
matic conditions of the region to be surveyed. Elevated sta-
tions should be occupied during good weather, as the lower sta-
tions, being more readily accessible and less often obscured by
clouds, may be successfully occupied at almost any time. Good
work may often be done at the lower stations when work on
the mountain peaks is impossible, owing to misty weather, snow,
or strong winds prevailing here, while the lower altitudes may
be free from either during the same time period.

Special attention should be given to a good selection of the
camera stations, with reference to the elevations and the dis-
tances of the terrene points that are to be determined, to the
focal length of the camera, the desirable degree of accu-
racy, the scale of the map, and the general character of the
country. A diversified and broken terrene will require more
stations to obtain a good topographic development and repre-
sentation on the map than a more regular section; the camera
stations, however, should be selected to obtain a full control
of all depressions, valleys, and general topographic features
from the smallest number of camera stations. Every feature
that is to find a representation on the map should have been
photographed from at least two, better three, stations. If a



GENERAL REMARKS ON PHOTOTOPOGRAPHY. 389

part of the terrene be visible from two stations only its icono-
metric location in horizontal plan may be accepted if its con-
trol points on the plan have been determined by good intersec-
tions (if the horizontal lines of direction intersect each other
at angles of 40 to 90 degrees), otherwise " vertical " intersections
or other means for checking the location of these points will
have to be adopted unless additional stations may be occupied,
while the party is still in the field, to obtain lines for a third inter-
section.

On the other hand, to reduce the number of photographic
plates that are to be transported, to simplify the iconometric
office work, and with due regard to the limited length of the
working-season in mountainous regions, it will be advisable
not to occupy more stations than are actually required for the
proper development of the terrene.

To secure the proper control for the location of the camera
stations on the map, at least three, better four, lines of direc-
tion to surrounding geodetic (triangulation) points should be
observed from each camera station. If that many triangula-
tion points be not visible from the station, that number of direc-
tions should be observed anyway, pointing on other well-defined
points (to supply the deficiency in triangulation points) that
may have been located before (as other camera stations), or
which may be located by later observations to be made at sta-
tions still to be occupied. Every station should be marked
with a signal before leaving, and such signal is to be observed
upon from stations subsequently occupied, observing both hori-
zontal and vertical angles.

Regarding the selection of the hours that are most favorable
for photographing the panorama views, one should be guided
principally by local conditions. Generally speaking, views of
identical regions should, if possible, be taken at the same time
of day and under similar atmospheric conditions, to facilitate
vlie recognition of identical points on the different views; the
actual shadows will then be alike in the different pictures. Pho-



3QO PHOTOTOPOGRAPHIC METHODS AND INSTRUMENTS.

tographing slopes altogether in shadow and exposing plates when
the sun is low should be avoided as far as possible. In the latter
case additional trouble may arise from the fact that one or more
pictures taken in the direction toward the sun may be affected
by halation; they will at best be more or less flat and will always
be deficient in details. Still, the phototopographer is seldom
privileged to select the most favorable time for making the expos-
ures, being governed by many considerations, having but a limited
time at his disposal, having to contend with moving cloud-masses,
inaccessibility of points, etc. Sometimes views will have to be
taken toward the sun if they are not to be dispensed with alto-
gether, but with the exercise of care and judgment photographs
may be obtained that will be of value for the iconometric plotting,
even when taken under such adverse conditions. The camera-
lens, however, should always be carefully shaded when taking
pictures under such untoward conditions.

It may generally be stated that the best results in mountainous
countries are obtained when the plates are exposed in the latter
part of the forenoon, the elevated peaks being mostly " hooded "
in clouds during the afternoon. Although these clouds fre-
quently disappear again late in the afternoon or toward evening,
still at this late hour all details of the valleys are obscured if
not perfectly hidden in a misty darkness.

When everything is favorable, the entire work at a camera
station may be finished within an hour and a half, or two hours
at the longest, and as three well-placed stations will control the
horizontal and vertical representation of an extended area, a
large territory may be reconnoitered phototopographically in a
comparatively short time.

The time consumption for accomplishing the field work of a
detailed phototopographic survey will be about the same as
for a more generalized survey, as about the same number of
photographs will be required in both cases. The difference,
however, appears at once during the execution of the office work.
In the first case the number of points to be plotted iconometrically



PRECISION OF THE " POLAR-ICONOMETRIC " METHOD. 391

may be very large, while in the latter case it will naturally be
very small, comprising points which characterize and control
the main features and forms of the terrene only.

We find, therefore, that outside of topographic reconnaissance
surveys in mountainous districts the phototopographic methods
are particularly well adapted for executing topographic pre-
liminary surveys made for that class of engineering works in
which the final and best location of the enterprise depends upon a
comparative study of the different sites as represented on the
topographic maps. Only a limited number of points would
have to be determined iconometrically to reach a decision whether
the site under consideration fulfills the required conditions. After
the best site has been determined upon, a more detailed and
accurate map may be constructed from the same field data
without having to supplement the original survey, either by
additional observations or photographs, every panorama view
giving the means to plot therefrom (iconometrically) almost an
unlimited number of terrene points.



13. Precision of the " Polar-iconometric " Method.

The desired degree of accuracy in a survey will generally
determine the class of instruments and the methods to be used
in its execution. To ascribe, therefore, the various surveying-
cameras and phototheodolites their proper places among survey-
ing-instruments, it will be of importance to know, or to ascertain,
what degree of precision may be obtainable with each repre-
sentative type of a special class. This has been done for some
of the special types that have been described in the preceding
chapters, and we will here enter upon a more general considera-
tion of the precision attainable in the so-called " polar " or
" radial " method of iconometric plotting.

We have seen that the graphic methods of phototopography



tTKJVERSITT



392 PHOTOTOPOGRAPHIC METHODS AND INSTRUMENTS.

are very similar to those of the plane table. It is generally
accepted that azimuthal errors in the directions of the " radials,"
drawn with the plane-table alidade on the plane-table sheet,
should not exceed 1.5 minutes in arc, and we shall see that when
the principal focal length of the camera does not fall below 1 50 mm.



Online LibraryJohn Adolphus FlemerAn elementary treatise on phototopographic methods and instruments, including a concise review of executed phototopographic surveys and of publicatins on this subject → online text (page 30 of 33)