1. The principle that how to film
prints

2. Contents
1. Photographic Film constriction
2. The Interaction Between The Film with The
Light
3. The Reaction Between Developer with The
Film
4. The Reaction Between The Film with The fixer
5.Safety On Working In The Dark Room

3. 1. photographic film construction
•Photographic film is sheet of transparent
plastic film base coated on one side with a
gelatin emulsion containing microscopically
small light-sensitive silver halide crystals.
• gelatin(is a translucent, colorless, brittle (when
dry), flavorless solid substance)
There are two types of films
•Panchromatic (sensitive to all colors).
orthochromatic (film sensitive to the three
primary colors, red, green, and blue). films

4. CONTI
•A typical photographic film contains tiny
silver halide salts such as silver bromide
(AgBr)
•*commonly found as "grains" or crystals
•The crystals are suspended in a gelatin
matrix.
•The silver bromide is in the form of
crystals, or grains,

5. Silver bromide(AgBr)

7. Parts of film
base and emulsion
Base
• made of a clear polyester material
•does not participate in the image-
forming
•clear, strong, consistent thickness
•Tinted pale blue or blue-gray
•coated on 1 or 2 sides with emulsion

8. Emulsion
•(single emulsion / double emulsion)
•Protective overcoat layered on top of
emulsion
•Emulsion is a gelatin containing the
film crystals
•Emulsion is the “active” layer of film
• Active for image forming
• Consists of many small silver halide
crystals suspended in gelatin.
•The gelatin supports, separates, and
protects the crystals.

9. Base and Emulsion

10. The interaction between the
film and the light
•These compounds of silver are crystalline
in nature and the crystal size is super tiny
with a slight yellow hue.
•When exposed to light, a micro speck of
pure silver forms. In other words, the
crystal starts to reduce (return to an not
united state).
•This is the reaction that happens when
the crystals are hit by a few photons (light).

11. Step 1: Light Activation
•It is not fully understood exactly what
happens during exposure but the energy
released when a photon of light strikes a
silver halide crystal frees an electron from
the bromide ion.
•The former bromide ion is released from
the crystal as bromine and is absorbed by
the gelatin

12. Step 2: Movement of electrons
The free electron moves through the
crystal to a 'sensitivity speck' caused
by imperfections in the crystal
structure or created during the
sensitizing process during
manufacture

13. Step 3: Deposition of Silver Ions
•This now negatively charged speck attracts
positive silver ions which are neutralized to
form silver atoms.
•If enough silver atoms form at a single point
then a latent image is created.
•The latent image is not visible, even under a
microscope so the only way to tell if it is
present is to chemically develop the film to
reveal the image

14. Exposure to a charged particle
A charged particle
passes through
silver bromide
crystals
Silver bromide
crystal（AgBr）
Deposition of
energy to the silver
bromide crystals
Latent image specks
Track
Formation of
Latent image
specks
Charged
particle( light
particle or
photon)
Gelatin
latent image
specks

15. Interaction of silver bromide with
light
Ag+Br- (crystal) + hv (radiation) -->
Ag+ + Br + e-
The silver ion can then combine with
the electron to produce a silver
atom.
Ag+ + e- --> Ag0

16. conti

17. conti

18. The free silver produced in the exposed silver
halide grains constitutes what is referred to
as the "latent image," which is later amplified
by the development process

19. 2. The reaction between developer and
the film
Development - The developing agent gives up
electrons to convert the silver halide grains to
metallic silver.
Grains that have been exposed to the radiation
develop more rapidly, but given enough time the
developer will convert all the silver ions into
silver metal.
Proper temperature control is needed to convert
exposed grains to pure silver while keeping
unexposed grains as silver halide crystals.

20. conti
A developer is a solution that has the
ability to recognize the difference
between exposed and unexposed silver
salts.
The developer, having identified
exposed silver salts reduces them to
their two component parts.
The silver component is reduced to
metallic silver and remains imbedded in
the gelatin.

21. Developer Solution
(6 Ingredients )
The halogen component is soluble in water and
dissolves away into the waters of the developer
solution
1. Reducing Agent: reduce exposed silver halide
to black metallic silver
-Hydroquinone (Blacks)
-Phenidone (Grays)
2. Activator: softens gelatin, maintains alkaline pH
(increase pH)
-Sodium Carbonate

22. Developer Solution
3. Hardener: prevents damage to the film
from over swelling of gelatin in
automatic processors.
-Gluteraldehyde
4. Preservative: Antioxidant that prevents
oxidation of developer
-Sodium Sulfite

23. Developer Solution
5. Restrainer: prevents chemical fog
protects crystals from chemicals
-Potassium Bromide
6. Solvent: dissolves & ionizes the
developer chemicals
-Water

24. 4. the reaction between the
film and the mixer
•Next the film is immersed in a fixing
bath.
•This bath is a solvent for silver salts
but not a solvent for metallic silver.
•Two fixing solutions are in common
usage, sodium thiosulfate and a
rapid acting ammonium thiosulfate.
•Often called hypo a name derived
from hyposulfite of soda.

25. Fixer Solution
(5 Ingredients)
1. Clearing Agent: dissolves
undeveloped silver halide
-Ammonium Thiosulfate
2. Tanning Agent: shrinks, hardens,
preserves emulsion
-Aluminum Salt

26. Fixer Solution
3. Activator: neutralizes developer,
maintains acidic pH (decrease pH)
-Acetic Acid
4. Preservative: prevents oxidation,
prolongs solution life
-Sodium Sulfite
5. Solvent: dissolves other
ingredients
-Water

27. Simplified Schematic Representation of
the Silver Halide Process

28. Wash & Dryer film
Wash: Provide thorough removal of
chemical solutions from the film.
-Archival film quality
Dryer: Removes water from film by blowing
warm, dry air
-Between 120 degrees & 130
degrees F

29. Anybody who is working in a darkroom should
follow these instructions and get themselves
familiar with these health and safety rules
5.Darkroom General Safety Rules:
•Limit access to the darkroom.
•Only approved persons should be allowed to
work in the room.
•Practice good housekeeping.
•Keep the work area clean and uncluttered to
prevent tripping over hazardous chemical bottles.
•Separate the wet and dry areas.
•Always segregate chemicals. (Don’t store acids
near reducer).

30. conti
•Use the least toxic chemicals
available.
• Avoid cyanides, heavy metals and
developers containing pyrocatechol
or pyrogallol when possible.
•Do not store chemicals on the floor.
•Do not eat, drink or smoke in the
darkroom.
•The darkroom should be well
ventilated.

31. conti
•Wear appropriate protective
equipment whenever possible, such
as gloves, goggles, etc.)
• Always wash hands with soap and
warm water after working with
chemicals.
•Know how to use emergency
equipment prior to an actual
emergency.
•Always Add Acid to water, never
water to acid.

32. conti
•Keep a spill kit in the darkroom.
•Do not use paper towels or saw
dust to clean up acid spills as this
may cause a fire.
•Pregnant women should not be
exposed to powdered developer.
•Store all chemicals in locations that
will minimize the chance of breakage
and splashing

33. conti
•Label all containers.
•Keep all containers and trays closed or covered
when not in use to prevent the release of toxic
gases.
•Do not wash any chemicals down the sink
(exceptions noted below).
• All spent chemicals should be placed into an
appropriate waste container. (A container the
same as the one the chemical was originally
shipped in is best).

34. Question

35. THANK YOU