Image Processing Flashcards
If film is exposed to white light or ionizing radiation, what 2 options can be used to prevent that?
- Daylight system – consists of an automatic film unloader that takes the sheet of film out of the cassette and moves it directly into a film processor.
- Darkroom - functions to protect the film from white light and ionizing radiation during handling and processing
Darkroom function
Protect film from:
Visible light
• Ionizing radiation
• Excess heat and humidity • Static electricity
• Pressure
• Chemical fumes
Film processing functions
Converts latent image to manifest image
• Preserve image for permanent storage
What are the 2 basic methods used for film processing?
Manual – film is transported through each step by hand.
• Automatic – electro-mechanical device that transports film through various solutions
Processing chemistry developer
Most important processing step
Converts latent image to manifest image
Uses oxidation/reduction reaction
Development
First stage in processing of the radiograph
Amplifies latent image by 100,000,000
Converts invisible latent image into visible form
Latent image
Bromide ions react with silver ions to form metallic silver ions, and eventually get a cluster of them
Developer or Reducing agents
Phenidone - Fast acting producing optical densities under 1.2
Hydroquinone - slow acting, producing optical densities above 1.2
Uses Synergism or Superadditivity
Most hazardous processing solution, very high pH
Accelerator, Activator, or Buffering Agents
Maintain alkaline medium
Soften and swell film emulsion - gives more area for develop solution to do its activity
PH scale
Developer should have a pH of 10-11.5
Restrained, regulator, anti-foggant, or starter
Restrains the action of developing agents to help prevent chemical fog
Preservative
Helps prevent premature oxidation
Premature oxidation can be caused by:
Aerial- contact with air
Internal - contact with other ingredients in developer
Photo - exposure to light
Hardener
Keeps film emulsion from sticking to rollers in processor
Weaker hardener than in fixer solution
Glutaralehyde is used
Solvent
Other components mixed with solvent, creates developer solution
Water is used
Sequestering agent
Used for developer solutions mixed from concentrate
Keeps impurities in tap water from oxidizing reducing agents
Ready or premix
Easier but more expensive
Concentrate
40% cheaper but less convenient
Must be mixed properly from kit
Developer activity factors
Solution Temperature
• Immersion Time
• Solution Concentration • Type of Chemicals
• Solution pH
• Exhaustion/Replenishment
2 most important factors for film processing
Time
Temperature
Optimum temperature range fo film processing
68-72 degrees Fahrenheit
Ideal time and temp
5 minutes @ 68 degrees Fahrenheit
What should be done when film is in the developer?
Agitate it to remove build up of halogen gas bubbles
If not done, uneven development can occur
Replenishment
Overtime, developer becomes exhausted
Fixer
Has 4 major functions:
1.stop further development
2. To clear the image
3. To fix image
4. To complete the process of hardening of the film emulsion
Reasons for replenishment
Oxidation occurs to quick
Acid compounds form
A lot of developer is consumed
Fixer components
Fixing agent - Removes unexposed and undeveloped silver halide crystals
Preservative - Helps recycle fixing agent
Acidifier - Provides an acid medium for the fixing agent so that it can remove the unexposed and undeveloped silver halide crystals.
Hardener or tanning agent - Permanently hardens film emulsion for long-term archival storage
• Hardening process is also called tanning
Sequestering agent - Helps prevent development of aluminum hydroxide
Solvent
Fixer is available in what?
Concentrate kit
Washing
Film must be washed well with water
Removes all thiosulfate complexes
Tap water is used
Incomplete wash causes retained hypo to react with silver
Drying
Surface water and most retained in emulsion layer should be removed
Manual processing
More time required
More space
Lower cost
Better image quality
Less quality control
Automatic processing
Shorter time required
Less space required
Higher cost
Chemical fog
Better quality control
Automatic processor main systems
Transport System
• Temperature Control System • Circulation System
• Replenishment System
• Dryer System
• Electrical System
Transport system
largest and most complex system
• Made up of many moving parts, so is most likely to break down • Controls Processing Time
Transport system consists of:
Roller subsystem
• Transport-rack subsystem
• Drive subsystem
Temperature control system
Regulates solution temp
Water controlled system
Thermostatically controlled-most common
Circulation system
Also known as recirculation and
filtration system
• Ensures complete chemistry mixing
• Provides uniform temperatures
• Provides equivalent of agitation
performed in manual processing
Replenishment system
Used to replenish developer and fixer solutions
Available in volume, and flood
Dryer system
Consists of 2 to 3 heating units
Electrical system
Distributes electrical power
Types of automatic processors
7 and 3 minute, 90,60,45 second
Multispeed
transport system speed can be varied to select different combinations of the above
