Photography relies on photochemical processes involving silver bromide in film. When light hits the film, it causes a chemical reaction where electrons are released from silver bromide crystals. This creates a latent image. Developing the film in a dark room with a safelight makes this latent image visible. Spectral sensitizers are added to silver bromide crystals to increase their sensitivity to different colors of light, allowing colored images to form.

1. Application of
photochemistry
(Photography)

2. Introduction
• Photochemical is caused by the chemical reaction of light.
• Photography is based on photochemical process.
• The chemical involved in photography is silver bromide (AgBr),
thiosulfate and real ion.
• photochemistry in photography works when the silver bromide,
which has high sensitivity to light, in the film of the camera, absorbs
the light when the picture is taken.
• thiosulfate dissolved the silver bromide that had been exposed to
light more easily than the one that had been kept in the dark.

3. • Silver bromide in photography

4. Photochemistry and involved with the
development of film
• Photochemistry is the process by which electromagnetic energy
causes chemical changes to matter.
• involved with the development of film because the chemical reactions
allow the images developed from the film to obtain the colours it has.

5. The components
• Each roll of film is comprised of 4 components:
• The Base: is the component that all the other layers and chemicals
within the roll of film is clung on to.
• The base is essential to the film because without it, the film’s
structure would be very frail and more prone to tear apart due to the
mechanical strain occurring inside the camera.
• The Adhesive: is the component that binds all the individual
photochemical layers together which in result binds these layers to
the base material of the film.

6. • The Emulsion: Is a light sensitive colloid. It is known as a colloid
because microscopically dispersed insoluble particles are suspended
throughout this layer. This layer consists of sub-micron sized grains of
silver halide crystals dispersed in a fluid (gelatin).
• This component of the film is vital because it holds key to the
photochemical processes occuring inside the film.
• The Supercoat: is a protective coating that keeps the film from being
damaged during the development of the film.

7. Silver-halide Crystals & Spectral sensitizers
• Manufactured by: combining silver-nitrate and halide salts (chloride,
bromide and iodide) in very intricate ways that result in the formation
of different sizes of crystals (grain-like).
• chemically modified on their surface to increase their light sensitivity.
• are only sensitive to the blue portion of the spectrum which is not
efficient in camera film because it only produces mere portions of the
image.
• The Structure: Crystal lattice of a silver bromide crystal -> contains
ions of Bromine (Br-) & Silver (Ag+).

8. • Film's exposure to light: extra electron from bromine ion is
releasedFree electron attaches to positively charged silver ion.
• Silver ion + free electron -> Metallic Silver.
• This reaction occurs all over the layers and planes of the emulsion
which creates a faded latent image on the film.

9. Spectral sensitizers
• added to the surface of silver-halide crystal because it gives them to
ability to be more sensitive to other colours of the visible spectrum
(blue, green & red light).
• Transforms faded latent image on film made by silver-halide crystal to
a visible image.

10. The Photochemical Process
• Before (When capturing the image): A short exposure image formed
by the lens of the film camera produces a slight chemical change
which is proportionate to the amount of light absorbed by each grain
of silver crystal halide at different intensities in the emulsion of the
film. An invisible latent image in the emulsion is then formed which
can be chemically developed into a visible photograph.
• During (The chemical reaction): The photochemical process involves
turning the invisible latent image into a visible latent image on the
film, this is completed through the chemical reaction of applying
spectral sensitizers to the surface of silver-halide crystals.

11. • Spectral sensitzer molecules attach to the silver-halide crystal.
• Transfer the energy from a red, green, or blue photon to the silver-
halide crystal as a photo-electron (photon) & silver atom is knocked of
of crystal lattice.
• After (The development):The film is then development in a dark
room which is a room that is almost completely dark but it is
illuminated with an amber light-brown light known as a safelight.

12. • The darkroom allows the processes of light sensitive materials such as
film, the safelight is very suitable for darkrooms and the development
of film because it provides illumination only from certain parts of the
visible spectrum to which the photographic image being produced is
almost completely insensitive towards.
• After the chemical process, spectral sensitization has been increased
so when the film is developed, colour will appear.
• When photographs are developed, they can appear more red than
blue or green or vice versa because a region of silver atoms may have
held a higher concentration of that certain colour during the chemical
reaction.

13. Created by
•
‫حافظ‬ ‫ناصر‬ ‫امنية‬
•
‫هللا‬ ‫فضل‬ ‫محمد‬ ‫اسراء‬
•
‫العظيم‬ ‫عبد‬ ‫محمد‬ ‫االء‬