1. Natural Light source;and 2. Artificial Light Source

1. Carbon Arc 2. Incandescent 3. Photoflood lamps 4. Fluorescent Lamps

Chapter 2 Flashcards by Joan Baludbod

Light This refers to:

Electromagnetic radiation ;and
Radiant Energy

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within the portion of the electromagnetic spectrum that can be perceived by the human eye

Electromagnetic radiation

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makes things visible is classified by the wavelength into a system known as the electromagnetic spectrum

Radiant Energy

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Natural Light source

Moon and Star;
Sunlight

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Source of Light

Natural Light source;and
Artificial Light Source

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It is when the sun sets, day turns into night and it becomes dark.

Moon and Star

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The most popular and mostly used light source of photographers. It is free and no need to be transported. But it is not always there where we want it. It is uncontrollable but can be controlled using the camera controls

Sunlight

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Classification According to it’s Intensity

Bright sunlight/ Distinct Sunlight
Hazy Sunlight
Dull Sunlight/Cloudy
Overcast Sky/ Cloud Bright
Heavy overcast/ Cloud Dull

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This is the direct sunlight striking the subject. It is the brightest of all, it is highly directional, images taken with distinct sun is characterized by extreme highlights and deep shadows and it provides the highest contrast in a picture

Bright sunlight/Distinct sun

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It is a hazy sunlight when the sun is covered by thin clouds but still clearly visible and it is illuminating your subject, it produces soft shadows and moderate highlight and contrast is also moderate, while rays are directional.

Hazy Sunlight

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Objects in open space cast no shadow. It is cloudy when the sun is shining bright but covered with thick moving clouds, other parts of the sky maybe clear, lighting is even throughout and not directional, it does not cast practical shadows on your subject and contrast is relatively fair.

Dull Sunlight/ Cloudy

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Sun is bright but not visible, light is soft and not directional, skies may be covered with stationary clouds and it provides no shadows and low contrast

Overcast Sky / Cloudy Bright

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This is practically the same as overcast sky but generally darker and light is dull. It provides very poor contrast and static cloud is so thick where one cannot tell the overhead position of the sun.

Heavy Overcast/Cloudy Dull

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Light sources of this category are man-made and are divided into the
continuous radiation and the short duration. Continuous radiation, those that can give illumination continuously, short Duration and it gives a brief flash of light produced by a burning metallic wire (flash bulb) or an electrical discharge through a gas – filled tube (electronic flash). There are different classifications

Artificial Light Source

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this refers to some units are portable battery operated and are easily carried and can meet the rugged and rigorous demand for field work

UV Lamp

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This refers to Light Amplification through Simulated Emission of
Radiation. By illuminating certain items with LASER, they would fluoresce or could be made to stand out in sharp contrast from their background. This was especially significant in locating dried biological items

LASER

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This refers to far more expensive alternative to forensic LASER. It uses a variety of band pass filters to provide a high intensity beam of non – coherent light.

Alternative Light Source (ALS)

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This refers to a wide variety of relatively inexpensive light sources which use filtered white light.

.Forensic Light Sources (FLS)

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Continues Radiation

Carbon Arc
Incandescent
Photoflood lamps
Fluorescent Lamps

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This refers to a pair of carbon rods connected in series with a resistance across direct current.

Carbon Arc

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This refers to a conducting filament enclosed by a glass bulb heated by the electric current until emits lights.

Incandescent

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This refers to lamps that can be placed up very high producing deep shadows underneath protruding surfaces, if subject is a person standing, he will appear gloomy and sombre. These can be placed to shine from below giving mysterious and strange effects of frights to observers of the picture.

Photoflood lamps

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This refers to illumination in an electric discharge lamp of the mercury – vapor type. The coating fluoresces and sends out light of low brilliance with visible zone.

Fluorescent Lamps

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Short Duration Radiation

Chemical Flash Lamp
Electronic Flash Lamp

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This refers to light that produces by the rapid burning of metal wire, foil or primer powders. To produce a rapid and complete burning, the bulb is charged with O2, the lamp flashed once.

Chemical Flash Lamp

This is consisting of a slender glass tube filled with a gas (Xenon), a high voltage electrical discharge is passed through coiled tube, causing the gas to glow.

Electronic Flash Lamp

Light Angles

1. Front Lighting 2. Side Lighting 3. Back Lighting 4. Overhead Lighting

Distinct sun is used as front lighting when it comes from behind the photographer. It is a common belief that photographs taken at early in the morning or late in the afternoon is better compared to photos taken in any other time of day. The light, when the sun is low, is oftentimes described as magical. Colors are warm, shadows are long, and subject glow with razor sharp clarity.

Front Lighting

This type of lighting happens mostly in the morning and afternoon when the sunlight hits the subject from either the right or left flank of the photographer. It brings out textures, patterns, and shapes of objects.

Side Lighting

This type of lighting happens when the sun strikes the subject from behind or when the sun is directly in front of the photographer. Light coming straight from the back of the subject in portrait produces a bright edged outlined around it. Backlighting also brings out shapes and good profile as well as silhouettes of your subjects

Back Lighting

This normally occurs at noontime where sun is directly above your subject. This angle of lighting is generally not recommended for taking portraits. Strong dark shadows are cast at the subjects’ eyes. However, it can be corrected with a fill – in flash.

Overhead Lighting

Theories of Light

1. Wavelength of Light 2. Quantum Theory

When incident light hits a medium, three things might happen, the light maybe:

• Reflected • Absorbed • Transmitted

It occurs whenever an object changes the direction of a light wave but does not allow the wave to pass through it. Reflected light maybe Specular or Diffused. When light strikes the surface and rebound it is said to be reflected, and it is called incident light. The angle which it strikes is called incident angle

REFLECTION

It is the change in direction of a wave due to a change in its speed. This is most commonly observed when a wave passes from one medium to another. Bending of light when passing from one medium to another.

REFRACTION

It is described as the apparent bending of waves around small obstacles and the spreading out of waves past small openings. It is also described as the bending of light when it hits a sharp edge of an opaque

DIFFRACTION

Examples of Diffraction

a. CD or DVD b. Hologram c. Interference d. Rectilinear e. Absorption f. Filtration g. Polarization h. Fluorescence i. Transmission

act as a diffraction grating to form the familiar rainbow pattern we see when looking at a disk;

CD or DVD

A picture that changes when looked at from different angles) on a credit card

Hologram

This refers to the color that can be produced by interference of light waves in thin film like soap bubbles or a film of oil floating in water.

Interference

This refers to the nature of light that normally travels in straight line.

Rectilinear

This refers to the nature of light to be absorbed in the process of dark surfaces.

Absorption

This refers to the character of light to be altered from its colorless into visible state.

Filtration

This refers to the process by which the vibration of light are confined to definite plane, the speed of light can be measured

Polarization

This happens when molecules of the fluorescent material absorb energy at one wavelength and radiate it at another wavelength.

Fluorescence

This refers to the light that passes through an object.

Transmission

Medium of Lights

1. Transparent objects 2. Translucent objects 3. Opaque Objects

It allows sufficient visible light to pass through them that the object on the other side may be clearly seen. It transmits 90% or more of the incident light.

Transparent objects

It allows light to pass, however diffuse it sufficiently that objects on the other side may not be clearly distinguished . In some cases the objects on the other side may be recognizable but sharp detail and outlines are obscured. It transmits 50% or less of the incident light

Translucent objects

It is so greatly diffuse the light that recognizing the object on the other side is very difficult if not impossible. It divert or absorb light.

Opaque Objects

Simplistically, we can think of light travelling as a wave. A typical wave form (e.g., ripples on the surface of water) has crests (or peaks) and troughs (or valleys).

Wavelength

The light that we see is only a part of a tremendous range of energy called the ?

Electromagnetic Spectrum

Kinds of light in electromagnetic spectrum

a. Visible Lights b. Invisible Lights

Visible Lights

Red Orange Yellow Green Blue Indigo Violet

It range from 685-605 mμ

RED

It range from 605- 585 mμ

ORANGE

It range from 585-560 mμ

YELLOW

It range from 560-475 mμ

GREEN

It range from 475-455 mμ

BLUE

It range from 455-440 mμ

INDIGO

It range from 440-405 mμ

VIOLET

The light that cannot be detected by the naked eye is the invisible spectrum. The left region of the visible light is called the ultra violet region. The right region of the visible light is called infrared region which are too long in wavelength to excite the retina of the eye. It is detected by the skin as heat.

Invisible Lights

Invisible Radiation with wavelength shorter than 400 mμ

1. Ultraviolet lights 2. X-ray 3. Gamma rays 4. Cosmic rays

It is used to photograph fingerprints on multi – colored background, documents that are altered chemically or over writings and detection of secret writings.

Ultraviolet lights

electromagnetic energy having a wavelength that ranges between 10 – 30 millimicrons.Objects which are opaque as seen by the naked eye can be penetrated by x –rays.To produce a shadow photograph of an internal structure of solid objects, x –rays is suitable.

X-ray

Used in recording or photographing objects hidden by opaque mediums

Gamma rays

high energy charged particles, originating in outer space, that travel at nearly the speed of light and strike the Earth from all directions. It also include high energy electrons, positrons, and other subatomic particles. usually refers to galactic cosmic rays, which originate in sources outside the solar system, distributed throughout our Milky Way galaxy.

Cosmic rays

Invisible Radiation with wavelength longer than 400 mμ

1. Infrared Light 2. Radio Waves 3. Microwaves 4. Hertzian Waves

lights having wave length greater than 700 millimicrons. It wavelength ranges from 700 – 800 millimicrons. It is not a color or any kind of red. It is an invisible rays and it is only detected by the human skin as heat. It is used in taking photographs of obliterated writing, burnt or dirty documents. Also known as “Blackout photography”.

Infrared light

These light waves have the longest wavelength of all lights. It is used for communicating through the modification and amplification of sound waves.

Radio Waves

excite the water molecules in food, heat them up, and pass the heat throughout the food. It can harm the body because it can heat the water molecules in deep tissues.

Microwaves

An electromagnetic wave produced by the oscillation of electricity in a conductor (as a radio antenna) and of a length ranging from a few millimeters to many kilometers.

Hertzian Waves

The presence of all color

WHITE

The absence of all colors or the absence of light

BLACK

Primary colors of light rays

1. Red 2. Green 3. Blue

Secondary/ Contemporary colors of light rays

1. Yellow 2. Cyan 3. Magenta

Light rays

1. Primary colors of light rays 2. Secondary/Contemporary colors of light rays 3. Color mixing of lights 4. Color addition 5. Color Subtraction

Coloring Matters

1. Primary colors of coloring Matters 2. Secondary colors of coloring Matters 3. Tertiary colors of coloring Matters 4. Color mixing of coloring Matters 5. Neutral Colors

Primary colors of coloring Matters

1. Red 2. Yellow 3. Blue

Secondary colors of coloring Matters

1. Orange 2. Green 3. Violet

Tertiary colors of coloring Matters

1. Yellow - orange 2. Yellow - Green 3. Blue - Green 4. Blue - Violet 5. Red - Violet 6. Red - Orange

Neutral Colors

1. Gray 2. Black

Qualities of Light

1. Intensity 2. Color 3. Direction 4. Contrast 5. Quality

The amount of light reflected by the performer and the background. Also referred to as quantity of light and it refers to how bright or dim the light source is.

INTENSITY

also known as the temperature of the light reflected by the performer and the background

COLOR

The light determines the length and location of the shadows cast by the performer and the three dimensional props around him.

DIRECTION

refers to the difference in brightness between the brightest and darkest parts of the image which is the contrast between highlight and shadow areas. Highlights are the brightest parts of the image and shadows are the darker regions of an image

CONTRAST

It is not something we can measure. It is, instead, something we describe based upon visual perception.

QUALITY

the most pertinent, particularly in the design of lenses. It is best illustrated by the dropping of stone in a pond of still water. The series of wave which travels outward from the center point are just like wave that travels in all direction from a source with equal velocity. This theory maybe used to illustrate reflection, interference, refraction, diffraction and polarization.

Wavelength Theory

Max Plank theorized in 1900 that light might be made up of little bundles of energy named quanta

Quantum Theory

He measured the speed of light in 1976

OLE ROMER

Forensic Light Source

1. Latent Fingerprint Detection 2. Bodily Fluids 3. Hair and Fibers 4. Questioned Documents

The primary application of a forensic light source is for enhancing the detection of latent fingerprints. The use of fluorescent enhancement processes that compliment a light source greatly increases the types of surfaces from which a latent fingerprint can be detected.

Latent Fingerprint Detection

It will actually glow under the light source illumination.

Bodily Fluids

It will also glow under UV or visible light and will stand out strongly for collection

Hair and Fibers

A tunable forensic light source can be used to identify slight variations in ink type by viewing ink responses as the color of the light is tuned through the visible and infrared regions.

Questioned Documents