how photography works (film photography)

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

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How Photography Works (Film Photography). A Lecture By: AMIT CHAWLA. Photographic Process. Photographic Process can be broadly divided into 3 major steps: Ray optics and How light forms images Film Processing Print Processing. How light forms images. Concept of PinHole Imaging. - PowerPoint PPT Presentation

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Page 1: How Photography Works (Film Photography)

How Photography WorksHow Photography Works(Film Photography)(Film Photography)

A Lecture By:A Lecture By:

AMIT CHAWLAAMIT CHAWLA

Page 2: How Photography Works (Film Photography)

Photographic Process

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

Page 3: How Photography Works (Film Photography)

How light forms images

Page 4: How Photography Works (Film Photography)

Concept of PinHole Imaging

Page 5: How Photography Works (Film Photography)

Refraction by Converging Lens

http://www.physics.uoguelph.ca/applets/Intro_physics/kisalev/java/clens/index.html

Page 6: How Photography Works (Film Photography)

Converging Prisms

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

Page 7: How Photography Works (Film Photography)

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.

Page 8: How Photography Works (Film Photography)

How light forms image on Film

Cross section of Black and White Negative Films.

1. Overcoating

2. Emulsion

3. Base

4. Antihalation  backing

5. Noncurl  coating

Page 9: How Photography Works (Film Photography)

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.

Page 10: How Photography Works (Film Photography)

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.

Page 11: How Photography Works (Film Photography)

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.

Page 12: How Photography Works (Film Photography)

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.

Page 13: How Photography Works (Film Photography)

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.

http://ffden-2.phys.uaf.edu/212_fall2003.web.dir/Mike_Kudenov%20/Film.htm

Page 14: How Photography Works (Film Photography)

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.

http://ffden-2.phys.uaf.edu/212_fall2003.web.dir/Mike_Kudenov%20/Film.htm