FSIAPIA: Processing of Latent Image

Gurney-Mott Theory

Only accepted theory about latent image formation

Latent image

The invisible change induced in the film after exposure and before processing; potential image, invisible image

Manifest image

Exist on film after exposure and after processing, visible image

Sensitivity center

Physical imperfection in the lattice of the emulsion layer that occurs during the film manufacturing process (inherent to the film)

Sensitivity speck

Electron trap

Sensitivity center

Latent image center or the focal point

Silver sulfite

A chemical contaminant responsible for the physical imperfection of the silver halide crystal

1. Point defect

2. Sensitivity speck/center

Types of imperfection

Point defect

Occurs when ions move out from the cubical lattice formation

Sensitivity speck/center (electron trap)

Occurs when silver ions are trapped because of chemical impurities in gelatin

Latent image center

Refers to the clumping or grouping of silver ions

Latent image center

Clumping of 4-10 silver atoms

Frankel defect

Physical imperfection, consist of interstitial silver ions and silver ion vacancies

1. Gurney-Mott Theory

2. Mitchell Theory

Two theories of latent image formation

GM theory

Indicates that X-rays…

• Before exposure, silver halide (AgBr and Ag…

Explain the Gurney-Mott Theory

Mitchell theory

1. Wetting

2. Developing

3. Stop bath

4. Fixer

5. Washing

6. Drying

What does the manual process of film processing involve?

Developing, fixing, washing, drying

What are the stages involved in the automatic process of film processing?

1. Master tank (water jacket)

2. Insert tank (2 - one for developer, one for fixer)

3. Water tank

4. Washing tank (Cascade compartment - 2 wash tanks for initial and final wash)

Manual processing tanks

1. Developer tank

2. Fixer tank

3. Water tank

Tanks in automatic processor

Latent/Potential Image

Refers to the invisible image that exists on film after it has been exposed but before it has been processed

Visible/Manifest Image

Composed of black metallic silver, exists on film after exposure and processing

Reduction - Oxidation

Oxidation Produces Electrons; Electrons are Used in Reduction

REDOX = EUR/OPE

REDOX = EUR/OPE

Electrons which is a product of oxidation from developer will be absorbed by the SHC which will be reduced in a simplified form (black metallic silver)

The developer has to undergo oxidation to produce electrons. The produced electrons will be used for reduction of SHC into black metallic silver.

Process of REDOX

Potassium - Auto; Sodium - Manual

PASM

Potassium

(can also be used for manual processing, but has higher concentration)

Liquid concentration for automatic processing

Sodium

(cannot be used for automatic processing, can cause damage to emulsion layer because it is powder)

Powder base for manual processing

Processing chemicals

Temperature, immersion time, pH, and specific gravity or concentration

Developer reacts based on what?

Convert latent image to manifest or visible image

Main function of developer solution

To amplify the amount of the metallic silver on the film by increasing the number of silver atoms on each latent image center (focal point of development)

Secondary function of developer solution

9.6 to 10.6 (alkalinic)

pH level of developer solution

Oxidation is necessary to release electrons but too much will

Presence of bromides indicate the presence of oxidation

1. Reducing agents

2. Activator

3. Restrainer

4. Preservative

5. Solvent

6. Other components

6 developer solution composition

Reducing agents

Also called developing agents

Reduce exposed AgBr crystals to black metallic silver

Function of developing/reducing agents

Hydroquinone, Elon, Metol, and Phenidone (HEMP)

Chemicals in reducing agents

Phenidone (automatic) Elon and Metol (manual)

• Build up detail quickly in 1st half of development process

• Fast reducing or fast developing agent

• Speed indicator - first to take effect as compared to hydroquinone

• Produces optical densities of 1.2; responsible for gray shades (Dmin)

• (MD - mid-density point or intermediate density or midrange density)

Hydroquinone

• Principal component or main component chemical of the developer

• Completes development process

• Contrast indicator

• Build up contrast slowly (slow reducing agents) during development period

• For both manual and automatic

• Sensitive to light and temperature

• Produces OD greater than 1.2

• DD (density difference - contrast) Dmax

Synergistic effect

A higher activity when two chemicals are working together

Activator (activates HEMP) / Alkalinizer (increases alkalinity) / Buffing Agent (maintains pH) / Accelerator (speeds up development) / Wetting Agent (swells and softens emulsion)

• Sodium hydroxide / bicarbonate and potassium hydroxide / bicarbonate

• Maintains alkalinity

• Provides necessary alkaline medium

• Swells the emulsion gelatin so that the reducing agents can attack the AgBr crystals

9.6-10.6

10-11.5 or

10-12

pH level of wetting agent

Buffing agent

Any chemical that maintains pH

Chemicals: boric acid and Na hydroxide

Purpose: some chemicals of developer are acidic, some are basic

Boric acid

Used to maintain the acidity of Phenidone, sodium bromide and dialdehyde, and glutaraldehyde

Sodium hydroxide

Used to maintain the alkalinity of all the chemicals that is not mentioned in the boric acid example

Wetting stage

First step during manual processing

To swell and soften the gelatin in order for the reducing agents to develop the film (SHC) through penetrating fairly

Function of wetting agent (water)

Activator agent

Swell the gelatin emulsion for the reducing agents to attack the SHC

Sodium hydroxide, sodium carbonate, and Kodalk or sodium metaborate

Chemicals in activator agent

Kodalk does not release oxygen and is considered the most available and widely used activator

Why is Kodalk the most widely used activator?

Sodium hydroxide and sodium carbonate release oxygen

Sodium hydroxide, sodium carbonate, and Kodalk

Chemicals for accelerator agent

Increases pH value

Maintain alkalinity

Provides necessary alkaline alkaline medium

Maintains 9.6 - 10.6 pH

Function of Alkalinizer agent

Restrainer

Grouped into starter, anti-fogging, and regulation solution

Control the activity of the reducing or developing agent (HEMP) or decreases activity of developing agent

Protect the unexposed SHC (underdeveloped)

Function of restrainer

Sodium bromide / iodide or potassium bromide / iodide - acidic chemical that balances HEM

• increases when solution is oxidized which means it contains a greater number of bromide

Chemicals for restrainer

Regulator or restrainer

Controls activity of reducing agents

Anti-foggant

Prevents fog formation (chemical or development fog) which is a veil of nonuniform density

Sodium…

Used only at first mixture due to the increased activity, therefore must not be added to developing solution during replenishment, as there is an increased number of bromides in oxidized solution

Benzothiosole

An organic restrainer (not considered a starter solution) which is added to PQ developer, must be replenished

Exclusively for Phenidone to prevent action of Phenidone on unexposed crystals, since it is not restrained by bromide

Where is benzothiosole used?

1956

Date, first roller transport system uses hardener

Preservative/Cycon

Same with fixer solution

Slows down rate of rapid oxidation (aerial) of reducing agents

Function of preservative

Sodium sulfite, potassium sulfite and Cycon (for both automatic and manual)

Chemicals in preservatives

The chemicals react with Quinone (byproduct of hydroquinone which is a dye) capable of staining the film and form colorless compound found on oxidized solution called hydroquinone monosulfate

Oxidation cannot be removed, but can be slowed down

Process of preservation

• Contain great affinity with oxygen (can control the oxygen)

• Stabilizer: promote balance or equilibrium of chemicals (usually Phenidone and hydroquinone)

• Antioxidant : prevents internal oxidation

Function of preservative

External oxidation

Photooxidation

Aerial oxidation

Internal oxidation

Oxidation

It will create air bubbles turning evaporation through oxidation

Pressurized water causes bubbles - artifacts

Why must chemical not be shaken?

Why must water hose not be used?

Distilled water - most appropriate to use since it is balanced or neutral

What is used for solvent?

Rainwater on developer solution - scale of pH is 6 (acidic)

in developer, activity is decreased

In fixer, activity is increased

Increase mAs for automatic processor

Increase immersion time for manual processing

What should be used if there is no distilled water?

Mineral water - scale of pH increases

In developer, activity increases

In fixer, activity decreases but does not affect the film (only affects archival quality)

Solution for automatic: decrease mAs

Solution for manual: decrease immersion time

Alkalinic water

Add sequestering agent (chelates, EDTA, or calgon)

Solvent: Tap water on developer solution

Calcium sludge (use sequestering agent to prevent calcium sludge when using tap water)

Oily substance that can precipitate the chemical at the bottom of the solution and prevent deposition of metallic deposit artifact or calcium deposit artifact, prevents scaling of tank

Dialdehyde or glutaraldehyde

-For automatic processor only

-controls activity of activator or swelling of emulsion

Chemicals for other components: hardener/tanning agents (weak and temporary)

Hardener/tanning agents

Added to developer solution to prevent excessive swelling of emulsion, and to reduce film transportation problems and preventing damage to the emulsion

Developer : weak or temporary

Fixer: strong/permanent

Emulsion pickoff pinholes

Actual holes in the image where the emulsion has been physically picked off the polyester base, and causes gelatin buildup caused by exhausted hardening agent

The roller contains the emulsion leading to sticky processor roller (impeded on crossover)

What causes jamming of film?

Prevents the precipitation of calcium sludge, oily substance and precipitate of aluminum (sa fixer)

Function of sequestering agents

Sequestering agents

Sodium hydroxide/carbonate

Stimulates uniform development

For manual processing, water only

Wetting agents

Antifrothant/anti-foaming

Partnered with sodium hydroxide and carbonate to prevent bubble formation in the solution, prevent aerial and external oxidation

Close-fitting lids

Mixing paddle - must be labeled for developer or fixer

Hose should not be used

Fungicides

Chemical: Chlorox

Fungi develop in complete darkness and moisture

Developer: sodium hydroxide/ carbonate, boric acid or salts

Fixer: acetic acid

Maintains pH

Buffer

Stop bath

2%, 1%, or 10%

Maintains the activity of the fixer solution by adding 10% acetic acid and neutralize the alkaline developer (stop development process)

The presence of acetic acid will not cause oxidation on the fixer but with the water rinse bath, the increase in H2O component of the fixer will decrease acidity

Considered as weak acid

Stop bath

Acid Rinse Bath

Another term for stop bath

bromides and hydroquinone monosulfates

Oxidized developer solution contains _____ and _____ _____