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How Photography Works (Film Photography)

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.

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How Photography Works (Film Photography)

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  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.htmhttp://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.htmhttp://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.

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