Exam Flashcards
A disc of transparent glass generally bounded by two spherical surfaces capable of
transforming an image.
Lens
basic function of a camera lens is to?
Gather light rays
• A lens that is thicker at the middle than at the edge.
• It gathers light rays and refracts them to meet in a certain point
Convex Lens (converging lens/ positive lens)
is thicker at the edges than at the center; light rays passing through a
diverging lens are vent outward.
Concave Lens (diverging/negative lens)
Simple lenses generally produce aberrated (imperfect) images which can be
corrected using
Compound lenses
Lens Speed is the largest opening of the diaphragm that the light can pass
through.
• is important in taking pictures in dim light
Lens speed
• A lens with larger maximum aperture (that is, a smaller f-number) is a fast lens
because it delivers more light intensity to the focal plane, allowing a faster
shutter speed
Fast lens
A smaller maximum aperture (larger maximum f – number) is slow lens because
it delivers less light intensity and requires a slower shutter speed.
Slow lens
This refers to the size of the image produced by lens depend upon factors –
camera – to – subject and focal length. The lens collects the rays reflection from each point
and brings them into focus at the focal plane. The lens, however, does not focus the rays
into an exact point representing the original, but a small circle or blur called circle of
confusion.
Image size
This refers to good lenses that are capable of reproducing circles of
confusion much smaller than 1/1000 of an inch. This permits the focal plane to be moved
forward or backward form the plane of critical focus to the point where the circles reach
1/1000 inch in diameter and the image begins to blur.
Depth of focus
Allowable movement of focal plane
Depth distance
This refers to the lens that is focused on an object at infinity, the
distance from the lens to the nearest object in sharp focus is called
Hyperfocal distance
This refers to the distance from the optical center of the lens to the focal
plane, when the lens is focused on infinity
Focal plane
This refers to the distance so far away that rays are considered parallel when
they reach the camera
Infinity
This refers to the point of convergence of the light ray
Real focus
This refers to the point where diverging rays would meet if their
directions were reversed.
Virtual focus
The distance between the lens (technically 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.
• Classification of Lens Based on Focal Length
Angle of view
A lens with a focal length equal to the diagonal measure of the image area
Lenses with focal lengths from 45 to 60 millimeters are normal lenses because they
produce an image that is approximately the same with the view angle of the human
eye which is 45 degrees
Normal lens
It has a shorter focal length than the normal lens. Hence, it covers a picture angle of
60 to 90 degrees. It enables photographing a widely extended scene from a close
proximity or within a confined area.
Wide angle lens
provides a field of view of 180 degrees or more.
• A 6 – millimeter fish – eye lens made by Nikon has a 220 – degree field of view that
Fish eye lens
Lens with longer focal length that constrict the field of view and decrease the depth
of field while greatly magnifying the image. e.g. 85mm, 100mm, 200mm, 300mm etc.
• Characteristics of Long Focal Length
• Provides an enlarged image of an object.
• Allows you to take close – up shots while keeping your distance (reach out like
telescope) to provide greatly enlarged of a distant object.
• Provides shallow dept of field.
Less than 45 degree
Telephoto lens
A special type of camera lens with variable focal length which can be adjusted
continuously by the movement of the variable focus lens.
• This lens allows quick adjustment to give a wider or narrower field of vision but
keeping the image in focus
Zoom lens
The failure of light rays to focus properly after they pass through a lens or reflect
from a mirror.
Aberration
The focusing at different points of light rays passing through different parts of
spherical lens.
• This aberration occurs because light hitting the outer parts of the lens is bent more
sharply and comes to a focus sooner than that passing through the middle.
Spherical aberration
The failure of different colored light rays to focus after passing through a lens.
• The focusing of light of different colors at different points resulting in a blurred image
Chromatic aberration
The inability of the lens to bring horizontal and vertical lines in the subject to the same
plane of focus in the image.
• Astigmatism occurs at the edge of the image; the image appears elliptical or crossshaped because of an irregularity in the curvature of the lens.
Astigmatism
It occurs when light falling obliquely on the lens and passing through different
circular zones is brought to a focus at different distances from the film plane.
• A spot of light appears to have a tail, rather like a comet.
Coma
The plane of sharpest focus becomes curved, not flat.
• It is caused by rays from the outer limits of the subject plane coming to focus nearer
to the lens than the axial rays.
Curvature of field
Causes the image of a straight line, at the edges of the field to bow in or out.
Distortion
Two types of distortion
Pincushion
Barrel
result of double reflection from inner lens surfaces.
• It exhibits self as a misty hazy or cloudy semi circular path of light
Flare
Bright spot on the film caused by stray light from worn shiny parts of the lens such as
the stops, shutter, lens mount or from inside the camera itself.
Mechanical flare
Most corrected lenses is coated with a substance which will reduce one type of flare
(optical) and which will also increase the optic’s ability to transmit light, thus
reducing light to loss
Light loss
It can be reduced or eliminated by using the proper lens, shade places on the front of
the lens or shield.
Stray lighy
This refers to colored disks of glass or gelatine which are placed in front
of the camera lens to improve the quality of pictures; homogenous mediums
which absorb different wavelengths of electromagnetic energy; these are dyed
gelatine sheets cemented between carefully selected glass
Filters
This refers to photographic filters that are used effectively when
photographing blood. When used outdoors, a blue filters will make the sky, or any blue
object, appear white in the photograph.
Blue filters
This refers to photographic filters that are used in place of blue
filters for photographing blood. Often, they work better than blue filters.
Green filters
This refers to photographic filters that are used to photograph
white cars; the details of the car will stand out.
Yellow filters
This refers to photographic filters that is used
toscreens out the violet end of the spectrum. It is placed in front of a lens and left there;
it will not only improve most of the police photographer’s work, it will also prevent the
lens from being scratched.
Ultra violet/UV filters
This refers to photographic filters that are used to cut
down light transmission. It does not affect the tonal quality of the scene. They are also
used to reduce the light intensity to prevent over exposure.
Neutral density filters
This refers to photographic a filter that is used primarily to
control light reflected from highly polished surfaces, metallic objects and others. It is very
useful in photographing many different vehicles in auto accidents. This is the only filter
that can increase the blue saturation in the sky in a color photograph without altering the
remaining colors in the scene.
Polarizing filters
This refers to photographic filters that are used to
remove excess bluishness from distant view outdoor
Hazy and skylight filters
This refers to photographic filters that are intended to alter
the response to the spectral sensitivity in terms of the naked eye
Correction filter
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
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
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.
Backing
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 curl
This refers to emulsion layer that consist of three
(or four) layers stacked one on top of another with filter in between each. 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
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. It is
also somewhat sensitive to green light but to such a slight degree that is not important
Red filter
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 a material which is sensitive to X – ray region
of the electromagnetic spectrum.
X-ray film
This refers to film that is sensitive to a single color
of light
Monochromatic
This refers to film that is more sensitive to blue rays of ligh
Blue sensitive film
This refers to film that is sensitive to UV rays only
Ultra - violet sensitive 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
This refers to film that is sensitive to UV rays,
blue and green colors but not to red. Reds are recorded as dark tones, while greens and
blues as light tones when printed. 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
Infrared 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. This sensitivity is expressed in numerical rating as ASA
Exposure Index.
Film speed
Types of speed ratings
Asa
Din
Iso
ASA 100 below – the finer the grain structure, the richer the color
saturation and more impressive the image sharpness. For color works ASA 25, 50 and 64
films are ideal in glamour photography but all require a high level of light.
Slow
ASA 100 and 200.
Medium
Above ASA 200 to 1600 – 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
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
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. 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
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
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 coater paper
This refers to coating that can be air – dried, needs large
volumes of water for effective washing that can be reduced with washing aid
(hypoclearing agent).
Fiber based papers
This refers to types based on
emulsion with slow emulsion speed; for contact printing; image size is the same as that
of the negatives; 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); about 100 to 1000
times as sensitive as chloride papers; they give black tones in metal hydroquinone
developers and take about 1 ½ minutes to develop at 18 – 20 degrees C; give neutral to
cold black tone which is only affected by development type and techniques
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 papers
This refers to grades of printing papers for extreme contrast negatives; the
low contrast in the sensitized paper counteracts the high contrast in the negative, to give
a new print
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
contras
Velox 3
This refers to grades of printing papers that provides sufficient contrast to
compensate for every weak contrast; it is useful in printing silhouettes and other such
pictures in which high contrast is desired.
Velox 4
This refers to grades of printing papers for flat negatives that are relatively
unprintable.
Velox 5
This refers to paper weight that is intended for
purposeswhich 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 weigjt
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.
Exposed film affects the silver halides but the change is invisible. Developing enables the
invisible images into form. This is performed by soaking the film in the Develope
Developing
developing solution). The chemical contents are
Reducer – metol – hydroquinone
b. Accelerator – borax, sodium carbonate, sodium hydroxide
c. Restrainer – potassium bromide
d. Preservative – sodium sulphite, sodium bisulphate
The removal of the traces of the developer as well as it helps
in the removal of excess or undeveloped silver halides. This process stops development
by neutralizing the effects of the developer. 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
The three forms of rinse bath are:
a. Water Rinse Bath
b. Acid Rinse Bath
c. Hardening Rinse Bath
Even after developing, the image is still invisible because the
silver halides are still present in the emulsion. Fixing bath is required to loosen the silver
halides from the unexposed halides so they can be washed away.
Fixing bath
Ingredients in fixing bath are
a. Fixer – hypo (sodium thiosulfate)
b. Neutralizer – acid (acetic acid)
c. Preservative – sodium sulfite
D. HARDERER - POTASSIUM ALUM
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
The most important chemical in any developing agent. It is the one
that reduces the exposed halides into visible metallic silver. The two chemicals mostly
used are: (1) hydroquinone and (2) Metol.
Educing agnts
The purposes of accelerators are to energize the reducing agents and
they soften and swell the emulsion to permit the developer to penetrate deeply and
quickly. The three kinds of accelerators are: Sodium Carbonate, Sodium
Hydroxide and Borax
Accelerators
The commonly used preservative is Sodium Sulfite. It prevents stain
and makes the developing solution more stable and long lasting
Preservative
This chemical restrains the action of the exposed areas of the film and
permits control of density and contrast. Potassium bromide is the agent generally used
for this purpose.
Restrainer
