FORENSIC 2 Flashcards
This refers to a cellulose tape or plate where silver salts are suspended that are capable of recording light.
FILM
It is only a fraction of an inch thick, yet it is made of many layers. It is a “Sensitized Material”.
FILM
The thickest part is a clear plastic base which holds the rest together.
FILM STRUCTURE
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
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
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
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
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
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
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
This refers to scratch resistant coating.
Top Coating
This refers to a sensitive to blue light only; green and red light passes through it without exposing the color
halides.
Blue Filter
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
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
This refers to a panchromatic layer, sensitive to blue and red.
Red Filter
This refers to plastic film base.
Film Base
According to Use
Black and White Film, Color Film, Chrome Film, X ray Film
This refers to film intended for B and W photography.
Black and white film
This refers to films that have name ending in Color – color negatives for prints.
Color Film
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
This refers to a material which is sensitive to X – ray region of the electromagnetic spectrum.
X – ray Film
According to Spectral Sensitivity (Color Sensitivity)
Monochromatic Film, Panchromatic Film, Orthochromatic Film, Infrared Film, Non - Chromatic
This refers to film that is sensitive to a single color of light
Monochromatic Film
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
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:
Special Film for Special Purposes:
- Contrast Process Panchromatic Film
2.Contrast Process Orthochromatic Film - Infra red film
- 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
- Emulsion Layer
- Baryta Layer
- 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
- Resin – coated (RC) papers
- 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
- Silver Chloride Papers
- Silver Bromide Papers
- Silver Chlorobromide
- 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
- Light Weight
- Single Weight
- 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
- Predevelopment Water Rinse
- Developing
- Stop Bath – Rinse Bath
- Fixing Bath or Fixing
- Washing
- 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