FORENSIC 2 Flashcards by Nic P

This refers to a cellulose tape or plate where silver salts are suspended that are capable of recording light.

FILM

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It is only a fraction of an inch thick, yet it is made of many layers. It is a “Sensitized Material”.

FILM

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The thickest part is a clear plastic base which holds the rest together.

FILM STRUCTURE

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This refers to top layer; scratch – resistant coating; gelatine coating; an over – coating composed of a thin
transparent layer of hard gelatine which helps protect the silver halide emulsion from scratches and abrasions

Top Coating/Varnish Coating/Protective Coating

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This refers to structure of film that composed of silver halides and gelatine – a layer composed of silver
compounds (which are light sensitive) and halogens (such as bromide, chloride, and iodide which is used in small
amounts, seldom made more than 5% with silver bromide in fast film emulsion).

Emulsion Layer/Inert Gelatin

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This refers to structure of film that is made of cellulose acetate or other materials such as paper, plastic, or
glass which supports the emulsion layer and is coated with a non – curl anti – halation backing.

Film Base/Backing/Base

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This refers to a black dye applied on the rear surface of the film, it absorbs light that may penetrate the
emulsion layer to prevent it from reflecting back to the emulsion thus making the mage sharper since it suppresses
double image, and prevents the appearance of halo formation in the photograph.

Anti – halation Backing/Anti – Curl

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This refers to emulsion layer that consist of three (or four) layers stacked one on top of another with filter
in between each.

Structure of Color Film

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These separate layers record the green blue and red values that go on making all colors, because
all colors can be made of mixtures of red, blue and green which are called primary colors.

Structure of Color Film

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Structure of Black – and – white film

Top Coating/Varnish Coating/Protective Coating
Emulsion Layer/Inert Gelatin
Film Base/Backing/Base
Anti – halation Backing/Anti – Curl
Structure of Color Film

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This refers to scratch resistant coating.

Top Coating

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This refers to a sensitive to blue light only; green and red light passes through it without exposing the color
halides.

Blue Filter

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This refers to Carey – lea silver suspended in gelatin – it is coated between the top and second layer to
absorb any penetrating blue light but allowing green and red light to pass through.

Yellow Filter

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This refers to a layer that is orthochromatic; the layer sensitive to blue light (which cannot reach it) and
green, but not to red; red light passes on the bottom of the emulsion layer.

Green Filter

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This refers to a panchromatic layer, sensitive to blue and red.

Red Filter

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This refers to plastic film base.

Film Base

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According to Use

Black and White Film, Color Film, Chrome Film, X ray Film

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This refers to film intended for B and W photography.

Black and white film

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This refers to films that have name ending in Color – color negatives for prints.

Color Film

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This refers to films with names ending in Chrome – for color transparency – for slides films that are exposed
by slides, mounted in a cardboard for slide projectors; reversal type.

Chrome Film

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This refers to a material which is sensitive to X – ray region of the electromagnetic spectrum.

X – ray Film

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According to Spectral Sensitivity (Color Sensitivity)

Monochromatic Film, Panchromatic Film, Orthochromatic Film, Infrared Film, Non - Chromatic

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This refers to film that is sensitive to a single color of light

Monochromatic Film

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This refers to film that is sensitive to ultra – violet rays, and all light found in the visible spectrum, especially
to blue and violet light, suitable for general use in the preparation of black – and – white photographs and most
commonly used in investigative photography because it produces the most natural recording of colors.

Panchromatic Film

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This refers to film that is sensitive to UV rays, blue and green colors but not to red.

Orthochromatic Film

Reds are recorded as dark tones, while greens and blues as light tones when printed.

Orthochromatic Film

This type of film is popular in the market as the Kodalith Film.

Orthochromatic Film

This refers to film that is sensitive to infra – red and ultra – Violet radiation, which is beyond the human eye’s sensitivity, also sensitive to all the colors found in the spectrum, and useful in penetrating haze because of its longer wavelength.

Infrared Film

It is useful in laboratory analysis of questionable documents; in the discovery of old or faded tattoos or areas where small objects are hidden under the skin; and in the construction of camera traps.

Infrared Film

it is used to copy black and white originals and to photographs colorless subjects when extreme contrast is needed.

Non – Chromatic

this refers to film that is sensitive to ultraviolet and blue – violet colors only, and may be used when natural radiation is not important.

Non – Chromatic

Two Main Types of Color Film

1.Color Reversal of Color Film 2. Color Negative Film

This refers to film that produces transparencies that can be mounted as slides and projected with a slide viewer or on a light box, and end in the word Chrome.

Color Reversal of Color Film

This refers to film that is used in making prints, end in the word Color.

Color Negative Film

This refers to film sensitivity to light. This higher the rating of the film, the more sensitive it will be.

Film Speed

Film Speed Rating – Types of speed ratings

ASA,DIN,ISO

ISO

(Americal Standards Association)

DIN

(Deutche Industries Normen)

ISO

(International organization for standardization)

(Combination of ASA and DIN)

ISO

ASA 100 below

SLOW

the finer the grain structure, the richer the color saturation and more impressive the image sharpness.

SLOW

ASA 100 and 200.

MEDIUM

Above ASA 200 to 1600

FAST

need less light. Feature coarser grain, weaker color and a slight reduction in image sharpness

FAST

ASA 3200 and 6400.

ULTRA FAST

Slow, medium speed fill will handle 90% of the picture needed in police photography.

Special Film for Special Purposes:

1. Contrast Process Panchromatic Film 2.Contrast Process Orthochromatic Film 3. Infra red film 4. Very High Speed

This refers to a fine grain film that gives sharp differences between black and white. It is used in copying documents and photographing fingerprints

Contrast Process Panchromatic Film

This refers to film that is similar to panchromatic, but it is much slower and more sensitive to blue than red light.

Contrast Process Orthochromatic Film

This refers to film that is sensitized with color dyes to make it possible to record only invisible infra – red heat waves, also sensitive to blue light, so special filters have to be put over the lens.

Infra – red Film

This refers to film that is particularly valuable for law enforcement purposes. It is labelled only with #2475. It is useful for taking pictures at night. It has an ASA 800 to 2000.

Very High Speed Film

FILM SIZES

110, 120, 126, 135, 220

This refers to film sizes for cartridge loading pocket cameras.

110

This refers to film sizes that give a picture that measure about 2/14 inches wide.

120

This refers to film sizes that is older and larger cartridge loading type,

126

This refers to film sizes that are commonly known as 35mm, so named because the film is 35mm wide.

135

It was originally for motion pictures and the size used in commercial theatres.

135

This refers to film sizes that are the same as 120’s but yields twice many exposures.

220

Structure of Photographic Paper

1. Emulsion Layer 2. Baryta Layer 3. Base

This refers to layer of photographic paper that contains silver halides suspended in gelatine; the layer making the paper light sensitive; emulsion maybe composed of silver chloride, silver bromide, or silver chlorobromide.

Emulsion Layer

This refers to layer of photographic paper that is a gelatine layer containing barite crystals (barium oxide) to increase the reflectivity of the paper; the layer that makes the film glossy.

Baryta Layer

This refers to layer of photographic paper that is made of hard paper which must be chemically pure; chemical content does not change or react with light or other chemicals during printing.

Base

This refers to the combination of its texture and finish; texture maybe smooth fine grained, or rough and finish maybe glossy (semi – matt) and matt.

Surface

Coating

1. Resin – coated (RC) papers 2. Fiber – based Papers

This refers to coating that is made up by using a layer of paper which is coated both sides with a synthetic polymer, usually polyethylene; forms the base on to which the emulsion is coated.

Resin – coated (RC) papers

This refers to coating that can be air – dried, needs large volumes of water for effective washing that can be reduced with washing aid.

Fiber – based Papers

Types Based on Emulsion Used

1. Silver Chloride Papers 2. Silver Bromide Papers 3. Silver Chlorobromide 4. Variable Contrast Paper

This refers to types based on emulsion with slow emulsion speed; for contact printing;

Silver Chloride Papers

they give blue black tones in a 65 – 68 degrees F to develop.

Silver Chloride Papers

This refers to types based on emulsion with fast emulsion speed; for projection printing (enlarging);

Silver Bromide Papers

at 18 – 20 degrees C;

Silver Bromide Papers

This refers to types based on emulsion that the slow is used for contact and the fast is used for enlargement/projection printing; they give an image tone from warm black to reddish brown, depending on length of exposure, type, dilution and duration of developer.

Silver Chlorobromide

This refers to types based on emulsion that classified by its own maker according to their own ideas; most of those being used confirm broadly with:

Variable Contrast Paper

This refers to contrast that used to tone down a very contrasty negative and produces a fairly normal print,

Low Contrast

This refers to contrast that is used to print normal or medium contrast negatives.

Normal or Medium Contrast

Grades of Printing Papers

Velox 0,1,2,3,4,5

This refers to grades of printing papers for extreme contrast negatives;

Velox 0

This refers to grades of printing papers for high contrast negative.

Velox 1

- This refers to grades of printing papers for printing normal contrast negatives.

Velox 2

This refers to grades of printing papers for negatives that have weak contrast.

Velox 3

This refers to grades of printing papers that provides sufficient contrast to compensate for every weak contrast;

Velox 4

This refers to grades of printing papers for flat negatives that are relatively unprintable.

Velox 5

Paper Weight

1. Light Weight 2. Single Weight 3. Double Weight

This refers to paper weight that is intended for purposes which involve folding.

Light Weight

This refers to paper weight for all ordinary photographic purposes.

Single Weight

This refers to paper weight for large prints because they stand up better rough treatment.

Double Weight

The theory of film development refers to the principle in photography that explains how the latent image in the exposed film is converted into a negative image (visible image).

Film Development

This theory provides that there are six (6) stages (two optional) of chemical processing needed to make the latent image become visible such that it can be printed to produce a photograph.

Film Development

Stages of Film Development

1. Predevelopment Water Rinse 2. Developing 3. Stop Bath – Rinse Bath 4. Fixing Bath or Fixing 5. Washing 6. Drying

This is done by simply soaking the film in water for 2 to 3 minutes while agitating the water container for every 20 seconds.

Predevelopment Water Rinse

Converting the exposed image on the film into actual image.

Developing

The removal of the traces of the developer as well as it helps in the removal of excess or undeveloped silver halides.

Stop Bath – Rinse Bath

This process stops development by neutralizing the effects of the developer.

Stop Bath – Rinse Bath

It is also necessary to minimize the staining effect of the developer and at the same time conserve to some extent the strength of the fixing solution.

Stop Bath – Rinse Bath

Even after developing, the image is still invisible because the silver halides are still present in the emulsion.

Fixing Bath or Fixing

This stage also removes the unexposed and undeveloped halides by converting them to soluble salts which may be washed from the emulsion.

Fixing Bath or Fixing

This is the final part of the processing cycle, which removes the residual chemicals and soluble silver compounds from the emulsion and reveals the image.

Washing

A disc of transparent glass generally bounded by two spherical surfaces capable of transforming an image

Lens

The eye of the camera is also the heart of the camera

Lens

Compose of 1 lens

Simple Lenses

It consist of two or more simple lenses fitted together

Compound Lenses

A lens that is thicker at the middle than at the edge

Convex lens

Farsightedness

Convex lens

It is thicker at the edge than at the center

Concave lens

Nearsightedness

Concave lens

Combination of lenses

Compound Lenses

Size of the image produced by lens depend upon factors camera to subject

Image size

Refers to the distance from the optical center of the lens to the focal plane, when the lens is focused on infinity

Focal plane

The distance between the lens from its rear nodal point and the focal plane when the lens is focused on infinity

Focal length

The size of the image formed by the lens

Magnification

The amount of the scene shown on a given size of film

Angle of view

Focal length equal to the diagonal measure of the image area

Standard or Normal Lens

Angle of view is 45 degrees to 60 degrees

Standard or Normal lens

It has a shorter focal length tham at the normal lens

Short focal lens or wide angle lens

Angle of view exceeds 75 degree's

Short focal lens or wide angle lens

A lens with extreme wide angles

Fish eye lens

Field of view of 180 degrees or more

Fish eye lens

Lens with longer focal length

Long or telephoto lens or narrow angle

Angle of view is less than 45 degrees

Long or telephoto lens or narrow angle

A special type of camera lens

Zoom lens

The failure of light

Aberration

The focusing at different points of light rays passing through different parts of spherical lens

Spherical aberration

The failure of different colored lights rays

Chromatic aberration

The inability of the lens to bring horizontal and vertical lines

Astigmatism

Occurs at the edge of the image

Astigmatism

It occurs when light falling obliquely on the lens and passing through different circular zone

Coma

A spot of light appears to have a tail, rather like a comet

Coma

The plane of sharpest focus becomes curved not flat

Curvature of fields

Causes the image of a straight line, at the edges of the field to bow in or out

Distortion

A result of double reflection from inner lens surfaces

Flare or optical flare

Clear at the bottom, graduating to a color at the top

Graduated filters

Recommended on a situation in which the sky part of a scene is much brighter than the foreground

Graduated filters

Turn bright points of light into the stars with upto 16 points

Starburst Filter

Increase contrast in black and white photograph. It let's light of its own color pass through the lens to the film but hold back certain other color

Color filter