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Questions and Answers
What is the most important consideration in selecting screen film?
What types of light do calcium tungstate screens emit?
Blue and blue violet light
Which type of film is sensitive to the entire visible light spectrum?
Blue-sensitive film requires an amber filter.
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The appropriate humidity level for film storage is around __%.
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What is the primary function of the developer in film processing?
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Which chemical is an antifog agent in the developer?
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Match the following developer components with their functions:
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To stop the action of development, __ acid is used.
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What are the main components of the fixer?
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Study Notes
Spectral Matching
- The most important factor in selecting screen film is ensuring a match in spectral absorption between the film and the screen.
- This ensures that the screen works at its most efficient level.
- Calcium Tungstate screens emit blue and blue-violet light.
- Rare-earth elements emit ultraviolet, blue, green and red light.
- All silver halide films respond to violet and blue light but not to green, yellow and red light unless they are spectrally sensitized with dyes.
Film Types
- Panchromatic film is sensitive to the entire visible light spectrum.
- Orthochromatic film is green sensitive.
- Blue-sensitive film is only sensitive to blue light.
Safelight and Film
- For blue-sensitive film, a amber filter is used (550nm wavelength).
- For green-sensitive and blue-sensitive film, a red filter is used (600nm wavelength).
Film Humidity
- Optimal film humidity is between 40-60%.
- Humidity above 60% leads to an increase in fog.
- Humidity below 40% leads to static artifacts.
Manual Processing Unit
- A master tank holds insert tanks.
- The master tank acts as a water jacket, providing space between insert tanks for rinsing and washing films.
- Insert tanks are removable containers for individual processing solutions (developer and fixer) and are spaced within the master tank.
Processing Chemicals
- Developer chemicals convert the latent image into a visible image.
- Fixer chemicals prevent the image from fading and ensure archival quality film.
Wetting Stage
- Wetting is the initial stage of film processing.
- Wetting agents, usually water, penetrate the gelatin of the emulsion causing it to swell.
- In automatic processors, the wetting agent is included in the developer.
Development Stage
- Development converts the latent image into a visible image.
- The developer's primary action is changing the silver ions of exposed crystals into metallic silver.
Developer Components
- Components of developers include:
- Developing agent: Phenidone/Metol (produces shades of gray) and Hydroquinone (produces black tones).
- Activator: Sodium carbonate (helps swell gelatin, controls pH).
- Restrainer: Potassium Bromide (antifog agent, protects unexposed crystals).
- Preservative: Sodium Sulfite (controls oxidation, maintains balance among developer components).
- Hardener: Glutaraldehyde (controls emulsion swelling, enhances archival quality).
- Sequestering agent: Chelates (removes metallic impurities, stabilizes developing agent).
- Solvent: Water (dissolves chemicals for use).
Alkali components of developers
- Developers contain alkali components (sodium carbonate and sodium hydroxide)
- Purpose of alkali components: enhance the action of the developing agent and control pH.
Developing Stage: Reduction & Oxidation
- Reduction - neutralizes a positive ion.
- Oxidation - opposite of reduction, produces electrons.
- Redox reaction - reduction and oxidation occur simultaneously.
Fixing Stage
- Fixing prevents the image from fading.
- Fixing chemicals produce film with archival quality.
Fixer Components
- Components of fixer chemicals include:
- Activator: Acetic Acid (neutralizes developer, stops its action).
- Fixing Agent: Ammonium Thiosulfate (removes undeveloped silver, clears the emulsion).
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Description
This quiz explores the different types of photographic film, their spectral sensitivities, and the importance of matching them with appropriate screens for optimal performance. Additionally, it covers safe lighting practices and the effects of humidity on film quality. Test your knowledge about the interplay between film and light.
