Sensitized Materials: Film Types & Sensitivity

• Sensitized material comprises films and papers with an emulsion containing silver halide.

Types of Sensitized Material: Film

• Film consists of light-sensitive silver halides randomly scattered within an animal gelatin layer.

Film Types Based on Speed (Light Sensitivity)

• Fast film is ideal in dim conditions due to its high light sensitivity.
• Fast film is not advisable because of graininess.
• Slow film requires longer light exposure for complete emulsion exposure and has fine silver halide grains.

Film Types Based on Spectral Sensitivity (Color Sensitivity)

• Spectral sensitivity defines the film emulsion's responsiveness to different light wavelengths.
• Monochromatic film is sensitive to a single color of light, like white and black.
• Blue Sensitive Film is specially treated to enhance sensitivity to blue light rays.
• Ultra-Violet Sensitive Film is sensitive only to UV rays.
• Panchromatic Film is sensitive to ultraviolet rays and all visible spectrum light, especially blue and violet.
• Orthochromatic Film is sensitive to UV rays and blue and green colors, excluding red and is similar to the KODALITH FILM.
• Infrared Film is sensitive to infrared and ultraviolet radiation beyond the human eye's sensitivity.
• Blue Sensitive film is sensitive to UV and blue rays.
• Panchromatic film is sensitive to UV, blue, green, and red colors.
• Infrared film is sensitive to UV, all colors, and infrared rays.

Sensitized Paper (Photographic Paper)

• Sensitized paper's final form is the photograph.
• Materials needed to produce a photograph, or positive print.
• These have an emulsion coated with opaque material.

Photographic Paper Types

• Silver Chloride Paper is used for contact printing and has low sensitivity, leading to slow printing.
• Silver Bromide Paper is sufficiently light-sensitive, suitable for enlargement for larger prints.
• Silver Chlorobromide Paper contains both silver chloride and bromide for projection printing.
• Variable Contrast Paper combines contrast ranges in one emulsion for varying colored light production.

Film Components

• Light-sensitive silver halide grains
• Gelatin binder
• Emulsion
• Plastic film base
• Anti-halation layer

Black & White Film Parts/Structure

• Top Coating (Gelatin Coating) is a transparent gelatin layer protecting the silver halide emulsion from scratches.
• Emulsion Layer contains silver salt and gelatin.
• Film Base is made of cellulose.
• Antihalation Backing is a dyed layer preventing light reflection and halation.

Black and White Film Layer Parts

• Gelatin anti-halation layer
• Anti-curl backing adhesion
• Promotion layer
• Film base
• Adhesion promotion layer
• Emulsion layers
• Gelatin protective coating

Colored Film Parts/Structure

• Top Layer is sensitive to blue light only, allowing green and red light to pass without exposing the color halide.
• Emulsion Layer.
• Blue Filter.
• Yellow Filter, often Carey Lea silver in gelatin, absorbs penetrating blue light, allowing green and red to pass through.
• Green Filter: Orthochromatic and sensitive to blue light and green.
• Antihalation Backing/Coating.
• Film Base is made of plastic.

Colored Film Layer Parts

• Base
• UV filter
• Blue Record
• Yellow Filter
• Green Record
• Red Record
• Base
• Anti-halation backing

Photographic Paper (EBB)

• Emulsion Layer contains minute silver suspended in gelatin.
• Baryta Layer is a gelatin layer with baryta crystals (barium oxide particles) for increased paper reflectivity.
• Base is made of hardened white paper.
• The base must be chemically pure to prevent interference with the chemical processes, and is available in single or double weight.

Modern Fiber Based Darkroom Printing Pape

• Supercoating
• Emulsion layer
• Baryta layer
• Paper base

Photopapers

• Granularity and Graininess of Film.
• This refers to the size of metallic silver grains developed on exposed film.
• Different indicators of emulsion speed exist.

Emulsion Speed

• Emulsion Speed includes FILM SPEED / EMULSION SPEED.

ASA (American Standards Association) Rating

• An ASA rating is expressed in an arithmetical value system.
• Higher numbers indicate more sensitive film.
• ASA ratings include 10, 20, 30, 40, 50, 100, 200, 400, 800, 1000.

DIN (Deutsche Industrie Normen) Rating

• A DIN rating is expressed logarithmically.
• Principle matches ASA with 3 degrees.
• DIN ratings consist of 12, 15, 18, 21, 24, 27, 30, 33.

. ISO (International Standards Organization) Rating

• ISO rating is expressed in a combined arithmetical (ASA) and logarithmic value (DIN).

Film Speed - ISO

• ISO rating measures a film's light sensitivity.
• High ISO films are better in low light or quicker shutter speeds.
• Standard ISO ratings: 100, 200, 400, 800, 1600, and 3200.
• Films with high ISO is called fast film.
• Film w/ low ISO is called slow films.
• ISO rating equals the ASA rating.

Printing

• Printing is the process of generating positive images from negatives, such as prints on paper.
• A photographic print is made by projecting light through a negative onto light-sensitive emulsion paper.

Types of Printing

• Contact Printing involves placing printing paper directly against the negative, emulsion to emulsion, to produce positive prints.
• Projection Printing enlarges positive prints by projecting the image.

Advantages of Projection Printing

• Enlarging over contact printing.
• Cropping the main negative area.
• Eliminating the unwanted.
• Using Dodging or Burning-In. Dodging prevents light, and Burning provides more exposure.
• Local fogging is achieved with small external like small penlights to darken select areas.
• Diffusers creating special effects altering image.
• Correcting image distortion is achieved by angling enlarger easel.

Enlarger Basics

• Enlarger is an enclosed light source.

Enlarger Types

• Condenser Enlarger has condensing lenses to evenly align and project light rays.
• Diffusion Enlarger diffuses light to evenly spread it over the negative's surface.

Common Enlarger Parts

• Enlarger Head contains a light source, condenser lens, negative holder, and lens.
• Lamp supplies light through the negative to expose photographic paper.
• Condenser Lens spreads light, typically using two convex lenses.
• Negative Carrier holds the negative flat, fitted between the light housing assembly and the lens.
• Lens Aperture controls the light passing through.
• Lens forms the image from the negative.
• Focusing Mechanism adjusts the lens's position to focus the projected image.
• Enlarger Column holds the enlarger head.
• Elevating Control Knob controls the size projected
• Base Board supports the enlarger and easel.

Photographic Processing Goals

• Sequence of chemical changes making
• Developing
• Stopping
• Fixing
• Washing
• Drying
• Exposure, Development of Black and White, Film
• Unused film in the camera
• Exposure of film to light (photons)
• Silver formation
• Development
• Fixing
• Washing

Photographic Solutions

• Developer causes silver halides to change to change to metallic silver.
• Modern developers contains agents and accelerators.
• Stop Bath/rinse bath takes 15-20 secs.
• It contains diluted acetic acid with water used to make photographs remain permanently.
• Restrainer is commonly potassium bromide.
• Preservative prevents oxidation.

General Types of Rinse Bath

• Water rinse bath- prevents the contamination of the film.
• Acid rinse is also a stop bath, and mix (1 1/2 oz with 28% acetic acid.
• Fixing Batch takes to fix batch (15 min to 20min)
• Wetting Agent reduces surface tension.
• Drying removes excess water.

Crime Scene Photography Purposes

• Crime scene photography is the scene's documentation.
• Provide a permanent record that can be used for trials and hearings.

General Classifications of Crime Scene Photography

• Outdoor Photography
• It has a geographical location
• It helps tracing
• External conditions
• Indoor Photography
• It has ingress and engress points, which can be adjacent.
• It helps tracing like tools.

Rules to Observe in Crime Scene Photography

• Don't disturb because it's cardinal.
• Get all the data.
• Pay attention to camera.

Photographing the Victim

• Take shots from every angle!
• Get details.

Photographing the Crime Scene

• Capture weapons with and without measurements, biological stains, personal properties, etc.

Photography Uses

• Photography in law enforcement
• Macro-photography
• Micro-photography
• Photomicography
• Infrared
• Ultraviolet