Physics Unit 3 Flashcards
Film Processing
Latent image has too few silver atoms to produce a visible image.
Processing multiplies the number of silver atoms at the sensitivity center making the image visible.
Automatic Processing
first automatic processor was introduced by Pako in 1943
Used special film hangers and dip tanks
Could process 120 films p/hr.
took approximately 40 minutes to process onefilm
1956 Kodak
developed the first roller transport system which advanced film processing significantly
1965 Kodak
introduced the first 90 second processor
possible because of advancements in chemistry and polyester film base
still widely used
1987 Konica
introduced a 45 second processor but this unit requires special chemicals and films
Manual Processing Sequence
Wetting- swells emulsion
Developing- converts latent image to visible image
Rinsing/stop bath- stops developer action
Fixing- preserves image
Washing- rinses chemicals
Drying- dries, that’s pretty much it.
Automatic Processing
Developer
Fixer
Wash
Dry
Processing Chemicals
Wetting
Wetting- causes emulsion to swell so processing chemicals can penetrate the emulsion
uses water
Water is the UNIVERSAL SOLVENT which all the chemicals used in processing can be dissolved into.
Processing Chemicals
Developer
Changes silver ions of exposed crystals into metallic silver
Provides electrons to sensitivity center of crystal to change silver ions into metallic silver
Silver ion is reduced to metallic silver
Reduction uses electrons, oxidation provides electrons
EUR-OPE:
Electrons Used during Reduction
Oxidation Provides Electrons
Silver Halide Crystals will not allow electrons in unless they have been exposed to radiation
Unexposed crystals have a negative exterior and a positive interior electron will be repelled
Silver halide crystals which have been exposed possess a “GATE” which allows electrons to enter and convert the silver ions intpo metallic silver
More ions at sensitivity speck the larger the gate.
4 Silver Atoms
there must be at least 4 silver atoms at the sensitivity center in order for the crystal to have an open gate.
Rinsing/ Stop Bath
Stops developer action by neutralizing the pH of the emulsion
In Fixer in automatic processor
Fixer
AKA hypo, thiosulfate, thio, clearing agent
Removes unexposed and underdeveloped silver halide crystals from the emulsion
Hypo retention is when some of the fixer remains in the emulsion and oxidizes over time causing the film to turn yellow
Washing
Removes as much of the developer and fixer as possible
Water, the universal solvent is used
Automatic Processing
Transport System Temperature Control System Circulation System Replenishment System Dryer System
Transport System
Film is inserted into the film tray and picked up by the entrance rollers.
Microswitch senses film and controls replenishment rate of chemicals
Shorter side of film should be up against the edge of the side rail so less processing chemical is used
Alternate sides of the film tray to prevent wear on rollers
Film is transported through processor by rollers through developer tank, fixer tank, water tank and dryer system.
1 inch transport rollers move film, master rollers, planetary rollers, and guide shoes are responsible for turning the film around
Temperature Control System
Regulates temperature of chemical tanks
Developer temperature is critical
Must be maintained at 95 degrees F
High temp will cause over development, low temp will cause under development
Water needs to be maintained at 90 degrees F
Circulation System
Agitation continually mixes the chemicals, maintains temperature, and aids exposure to chemicals.
Continuously pumps developer and fixer
Developer is filtered to remove trapped bits of emulsion, unnecessary in fixer
Water is an open system, fresh tap water is pumped in at a rate of 3 gal/min
Replenishment System
Some of the chemical is absorbed into the emulsion of the film, some is carried over into the next tank.
Replenishment system replaces used chemicals
Microswitch controls how much replacement chemical is needed
Approx 60-70 ml of developer and 100-110 ml of fixer is used for every 14 inches of film developed
Water is continuously replenished
Dryer System
Dries film uses blower fan, warm air on both sides
Hot, moist chemical air is exhausted externally
Moist film is often caused by depleted hardener in the fixer.
Wet film can pick up dust, causing artifacts.
