DEVELOPING THE NEGATIVE
After exposure, the film or plate shows no visible change but the
“latent image” is there and by the aid of suitable chemicals and
solutions it can be brought out and made visible or in other words be
“developed.” Such solutions are termed developers.
CHEMICAL PROCESS. This consists in the removal of the bromine or
chlorine from the silver bromide or silver chloride of the emulsion
where the light has acted, so as to leave the grains of metallic silver
which constitute the photographic image.
Of the _developing agents_ which are capable of bringing out the image,
pyro, hydroquinone and Elon are perhaps the most commonly used for
negatives, although Elon is seldom used except in connection with one
or the other.
Although one of the oldest developers, pyro has long been considered
one of the best for the development of films and plates. It surpasses
other developers in the control it gives over the printing quality
of negatives as the color can easily be varied from a blue-black to
a slightly olive or yellowish tone. A slight stain image in addition
to the silver image is desirable as thus the negatives will not need
to be so dense as though they were blue-black. The present tendency
is to use pyro either in connection with Elon or with Elon and
hydroquinone. Beginners are likely to get the negatives a too decided
yellow; also pyro if somewhat oxidized will stain the finger nails. An
Elon-Hydroquinone combination is one of the most popular developers,
and being non-staining it is especially good for tray development.
A solution of pyro, Elon, or hydroquinone and water, will develop so
slowly that an _alkali_ such as sodium carbonate is added to speed
up the action. In the presence of an alkali, however, the developing
agent quickly oxidizes, making the solution somewhat colored. To
prevent this oxidation, a _preservative_ such as sodium sulphite is
added which keeps the developer clear without otherwise affecting its
properties. In order to minimize the tendency to fog (the development
of the unexposed grains of silver salts), a trace of potassium bromide,
a _restrainer_, is usually added.
TANK DEVELOPMENT
[Illustration: Fig. 8]
Within recent years the tank method has come to be preferred by the
majority of workers. If _roll film_ is being used, a special tank
developing machine consisting of a wooden box, a lightproof apron,
transferring reel, and metal solution cup will be necessary (Fig. 8).
No dark room is required. The film is wound into the apron according
to instructions and transferred to the solution cup where it is
left in the developer for a predetermined time. This is a logical
scientific method, development being continued for a definite time in
a solution of a given strength at a known temperature. It will produce
a technically correct negative and in the hands of the average person
will no doubt give the highest percentage of good results. If the
exposure is at all within the latitude of the film, the negatives will
be of proper contrast, differing in density according to the exposure
and although requiring different printing times will give prints of
similar quality.
_Film packs_ may also be developed in special tanks but a dark room is
necessary when loading them into the tank.
_Cut films_ and _plates_ are usually developed in open tanks and this
operation must be carried on in the dark room. The work may be done
either by the time and temperature system or the inspection method.
TRAY DEVELOPMENT
Tray development is not usually considered as convenient a method as
tank development but it has its advantages and is used by many workers.
Not only does it give an insight into the actual process, but it
affords an opportunity for the pictorial worker to secure results other
than an exact representation of the subject. Tray development must
be carried on in a dark room which is entirely free from white light
and which is illuminated only by a light such as given by a Brownie
Safelight Lamp when fitted with a Series 2 Safelight.[6]
[Footnote 6: Described in _Modern Dark Room Illumination_, Eastman
Kodak Co.]
Four trays are necessary, one for clear water, one for the developer,
one for a rinse bath, and one for the fixing bath.
Many workers prefer to purchase their chemicals made up in small
packages and ready for use with only the addition of water. This is a
very convenient method. Others are interested more in the science of
photography, and prefer to make up their own solutions from formulas.
Of the many good formulas available but one will be given here[7]:
[Footnote 7: Those who are interested in preparing other types of
formulas should have a copy of _Elementary Photographic Chemistry_
which can be obtained free from the Eastman Kodak Co., Rochester, N. Y.]
_Elon-Hydroquinone Tray Developer_
Water (about 125° F.) 8 ounces
Elon 22 grains
Sodium sulphite 1½ ounces
Sodium bisulphite 15 grains
Hydroquinone 42 grains
Sodium carbonate 82 grains
Potassium bromide 12 grains
Water to make 16 ounces
For use dilute with equal parts of water. The temperature should be 65
degrees Fahrenheit.
_Development._ If roll film is being used it is first detached from
the red paper on the roll, and then, one end being held in each hand,
it is passed face down through a tray of clear water several times to
eliminate air bubbles and to prevent curling. Next it is passed back
and forth through the developer in the same manner, this motion being
continued until development is complete.
Ordinarily the films should remain in the developer until the picture
is about faded out on the side where it first appeared and begins to
show quite well on the back. Longer development will not only make
the negative denser but will result in more contrast or a greater
difference in density between the highlights and shadows. Therefore
development should be continued until the negative is of the proper
density and contrast to give good prints on the type of printing paper
which is being used. Naturally it will take some experience to know
just when the correct point is reached. The negatives may be examined
by holding them up in front of the safelight lamp but they should not
be held there for more than a few seconds at a time.
Because of the extra transparent coating on film packs, the purpose
of which is to lessen the possibility of scratching the emulsion
on drawing the tabs, about 1–3 longer development is required than
for roll film. Super-speed film also requires longer development.
Panchromatic film, being sensitive to all colors, must be developed in
total darkness or by the aid of a deep green light.
_Rinsing._ When developed, films are rinsed for a few seconds in clear
water and then transferred to the fixing bath. The following rinse bath
may be used instead of clear water and has the advantage that it will
not only harden the films but will stop development at once.
Water 16 ounces
Potassium chrome alum ½ ounce
The negatives should be left in this bath for two or three minutes,
being moved about especially when first being immersed. The hardening
bath should be renewed frequently.
_Fixing._ After the negatives are developed the particles of silver
bromide which were not affected by the light are still sensitive and so
must be removed by a process called “fixation.” Here the hypo (sodium
thiosulphate) combines with the unexposed grains of silver bromide or
other silver salts to form a compound which is soluble in water and
therefore which can be removed by washing.
Either a chrome alum fixing bath or an acetic acid fixing bath may be
used, but the latter will be given here as this formula is suitable for
prints as well as negatives.
_Acetic Acid Fixing Bath_
A
Hypo 16 ounces
Water to make 64 ounces
When thoroughly dissolved, add
the following hardening solution:
Water (about 125° F.) 5 ounces
Sodium sulphite 1 ounce
Acetic acid (28%) 3 ounces
Potassium alum 1 ounce
The chemicals should be dissolved in the order given using water at
about 125° F. Be sure that the sodium sulphite has completely dissolved
before adding the acetic acid. After the sulphite-acid solution has
been thoroughly mixed, add the potassium alum and stir until completely
dissolved. Add the cold hardener solution (B) slowly to the cold hypo
solution (A), stirring the latter continually.
The negatives when first being placed in the fixing bath should be
moved about for a few seconds and then occasionally during the entire
time of fixation. This should be for about 15 minutes or for twice as
long as it takes to clear them of the white milky appearance. If not
kept separated properly or if removed too soon the negatives will later
discolor, probably showing yellow stain. Sixty-four ounces of this
bath will completely fix the equivalent of 200 3¼ x 5½ negatives if the
Alum Rinse Bath is used.
_Washing._ When removed from the fixing bath, negatives contain in the
gelatin a number of chemicals which must be removed if permanency is to
be assured. These include the hypo and other chemicals of the fixing
and hardening bath and also other compounds formed by the reaction
between the hypo and silver salts, and also possibly some carried over
from the developer. Washing should be for 30 minutes in running water
or for five minutes each in six changes of water.
_Drying._ Superfluous water together with any grains of dirt from the
wash water should be removed from the film or plate by swabbing gently
with absorbent cotton which has been saturated with water. Roll film
may be hung up to dry in such a way that neither side touches anything.
Drying should take place where there is circulation of warm, dry air,
but not in the sunlight or where the temperature is too high or the
emulsion may melt. Neither should the negatives be dried in a dusty
location as any specks of dust will show up as white spots when the
negatives are printed.
NEGATIVE DEFECTS
After the process of development is complete and the negatives are dry,
it may be found that some of them have been underexposed or overexposed
or underdeveloped or overdeveloped. The following table indicates
the results that should be expected from variations in exposure and
development.
Exposure Development Result
Under Under Very thin and weak, only highlights
visible.
Under Normal Thin, shadow detail weak or
lacking.
Under Over Thin shadows, dense highlights,
very contrasty, often fog.
Normal Under Thin, flat, detail throughout but
weak.
Normal Normal Correct density and contrast,
good detail in all parts.
Normal Over Rather dense with too much contrast;
detail may be obscured in highlights.
Over Under Somewhat thin, very flat, full
detail.
Over Normal Rather dense, somewhat flat,
plenty of detail in all parts.
Over Over Very black or nearly opaque,
shadows too heavy, detail lost in
the highlights.
Sometimes negatives are defective in some way and need treatment
before being printed. Those that are too thin and flat, having a
short scale of contrast as the result of underdevelopment, should be
_intensified_. On the other hand if the negatives have been overexposed
or overdeveloped they should be _reduced_. Formulas for these processes
are given in _Elementary Photographic Chemistry_.