1. How Photography Works
(Film Photography)
A Lecture By:
AMIT CHAWLA

2. Photographic Process
 Photographic Process can be broadly divided
into 3 major steps:
– Ray optics and How light forms images
– Film Processing
– Print Processing

3. How light forms images

4. Concept of PinHole Imaging

5. Refraction by Converging Lens
http://www.physics.uoguelph.ca/applets/Intro_physics/
kisalev/java/clens/index.html

6. Converging Prisms
In practical
photography & in
cameras instead of
single Convex Lens
we use number of
PRISMS with
combined
convergence effect.

7. Converging Prisms in Professional
Lenses
 In professional Lenses not a single convex lens
or a convex prism, instead a combination of
many lens elements are combined together to
achieve an overall converging effect.

8. How light
forms image
on Film
 Cross section of Black and White Negative Films.
 Overcoating
 Emulsion
 Base
 Antihalation backing
 Noncurl coating

9. 1. Overcoating
 The overcoating protects film from friction,
scratches, or abrasions before development.
 The overcoating is a clear, gelatin layer that is
sometimes called the antiabrasion layer.

10. Emulsion & Base
2. Emultion - Thin layer of gelatin that
suspends and supports the light-sensitive
silver halides.
3. Base -This supports or holds the emulsion in
place. The base may be transparent,
translucent, or opaque, depending upon how the
recorded image is to be used. The base is
generally made of a cellulose acetate.

11. 4. Antihalation backing-
 The antihalation backing prevents light from
reflecting from the base back into the emulsion.
The antihalation dye is sometimes
incorporated in the anticurl backing. The dye
used to eliminate halation is a color to which the
emulsion is least sensitive. This dye is water
soluble and is com- pletely dissolved during
processing.

12. 5. Noncurl coating
 Noncurl coating is a hardened gelatin, about
the same thickness as the emulsion, and is
applied to the back of the film. A film emulsion
swells when wet and shrinks when dry. This
contraction produces a strain on a film base
because it is highly flexible. The noncurl coating
prevents the film from curling during the
drying process.

13. http://ffden-2.phys.uaf.edu/212_fall2003.web.dir/Mike_Kudenov%20/Film.htm
Structure of AgBr
 This lattice contains
ions of bromine and
silver (Br- and Ag+).
When incoming light
hits this crystal lattice,
the extra electron
contained on the
bromide ion is
released.

14. http://ffden-2.phys.uaf.edu/212_fall2003.web.dir/Mike_Kudenov%20/Film.htm
Reaction of photons on AgBr
 This free electron then jumps
from the now bromine atom to
the positively charged silver
ion. As a consequence of this
electron coming into contact
and binding to the silver ion,
the silver ion is transformed
into metallic silver (Ag). This
creates a small region of
silver metal.