GEMINI CRIMINOLOGY ONLINE REVIEW AND TRAINING CENTER P E N E T E E A P Dr. MANUEL V JAUDIAN, LLB. PhD ETEEAP DIRECTOR NOTES COMPILED AND EDITED BY: PROF. HERMOGENES MALAGAMBA POLICE PHOTOGRAPHY Photography is the production of visible images by using the action of light on a sensitized material. The word photography was derived from two Greek terms PHOTO which means light and GRAPHY which means to write . Thus, literally, photography means to draw with light. SPEED OF LIGHT The speed of light, measured in a vacuum is 299, 792.5 km/sec (approximately 186,281 miles/sec / 186,000). BEHAVIOR OF LIGHT INTERFERENCE - Any phenomenon having a periodic disturbance of some sort and travels outward from a source is called a wave. To understand how energy can travels in waves, think of a wooden log floating in the ocean. Light maybe visualized as such as the high points are called crest while the low points are called troughs. The distance between two successive crest and troughs is called a wavelength. DIFFRACTION – light in space and not within the gravitational field of any object travels in a straight line. The bending of light around an object gives rise to the phenomenon called diffraction. This phenomenon is responsible for the partial illumination of object parts not directly in the path of the light. THE LAW OF REFLECTION – refers to the rebounding or deflection of light. The angle of reflection depends upon the angle of the light striking the material, which is referred to as the angle of incidence. THE LAW OF REFRACTION – when the material in the path of the light is transparent a change in the direction of the light occurs. THE ELECTROMAGNETIC SPECTRUM By using a prism made of glass or plastic, it is possible to see the colors that made up the sunlight. The colors separated in this way are called a spectrum. Another way to see the spectrum of sunlight is to look at a rainbow. The light is bend as observed, and because some of wavelengths bend more than others, the colors are separated. The violet rays are bent the most, and the red rays least. SOURCES OF LIGHT NATURAL LIGHT The source of all daylight is the sun. The combination of color and contrast ascertains the quality of the daylight. The lighting contrast depends upon the sunlight available in the daylight, when clouds do not cover the sun. Color of the daylight will also affect the appearance of the objects being photographed specially in color photography. Some of the factors affecting the color of the daylight: a) atmospheric vapor b) atmospheric dust c) reflected light reached the objects and directly coming from the source. Daylight maybe classified according to its intensity. They are: a) Bright sunlight b) Hazy sunlight c) Dull sunlight. These classifications are modified by the film manufacturers like a) Open bright sunlight b) Under shade bright sunlight c) Hazy sunlight d) Cloudy bright sunlight e) Cloudy dull sunlight. ARTIFICIAL LIGHT Almost all artificial light sources can be used in photographing of objects, as long as the light is capable of exposing the sensitized materials (film). Some of the artificial lights are electronic flash, photoflood lamp, fluorescent lamp, and Infrared and Ultra-Violet lamp. COLORS OF LIGHT FOUND IN VISIBLE SPECTRUM Visible Spectrum - a small part of the electromagnetic spectrum where the visible light is found, the portion of the electromagnetic spectrum that affect the human sense of sight. Visible light includes all those radiation having a wavelength ranging from 400 – 700 mu. COLOR Primary Colors Approximate Wavelength A. Red (longest wavelength) 700 mu B. Blue 450 mu C. Green 550 mu Complementary Colors A. Magenta (shortest wavelength) 400 B. Cyan 500 C. Yellow 590 Neutral Color A. Gray B. White C. Black COLOR MIXING 1. Color Addition R+B+G = W R+B= M M+Y= R R+G= Y Y+C= B B+G= C Y+C= G 2. Color Subtraction W-R= C W-C=R C-G=B W-B=Y W-Y=B Y-G=R W-G=M W-M=G Y-R=G PRIMARY AND SECONDARY COLORS The three primary colors in light are red, green and blue. White light can be made by mixing red, blue and green. The process of making colors by mixing primary colors of light is called addition, because one color is added to another. OPTICS Optics is the study of light. It is concerned with the nature of light and the way it behaves in optical instruments. ATTRIBUTE OF COLORS Radiant energy within a limited frequency range has the property of stimulating the retina of the eye to create color sensation, which the brain interprets. Radiant energy, which has this property, is called light, the physical stimulus of vision. Color can be defined in qualitative terms according to certain psychological attributes. These attributes are hue, brightness and saturation. Hue is the attributes of chromatic colors, which distinguishes them from achromatic colors. MEDIUM OF LIGHT TRANSPARENT OBJECTS – mediums that merely slow down the speed of light but allow to pass freely in other respects, transmit 90% or more of the incident light. TRANSLUCENT OBJECTS – mediums that allow light to pass through it in such a way that the outline of the source of light is not clearly visible, transmit 50% or less of the incident light. OPAQUE OBJECTS – A medium that divert or absorb light, but does not allow lights to pass though, they absorb most of the light while reflecting some of it. THE RAT LAW When incident light hits a medium, three things might happen, the light maybe: A. Reflected B. Absorbed C. Transmitted MECHANICAL DEVICE (CAMERA) The principle of photography are derived from science and the images on the film or paper made by the rays or light through the camera are dependent on the same general laws which produces images upon the retina through the lens which produce images upon the retina through the lens of the eye. A camera basically is nothing more than a light tight box with pinholes or lens, a shutter at one end and a holder of the sensitized material at one end. While there is various kind of camera from the simplest in construction (the box type) to the most complicated, all operate in the same principle. The exposure of the sensitized material to light is controlled by the lens and its aperture and the shutter through its speed in opening and closing the lens to light. CAMERA TYPES THE PINHOLE CAMERA - The simplest camera is a pinhole camera, which consists of a box with a small hole in one of its sides. To produce a sharp image, the hole must be very small and this restricts the amount of light entering the camera. Quite a long time may be necessary to let enough light through to affect the film and this causes problems because if the subject moves the picture will be blurred. It is impossible to photograph anything like a moving car or a galloping horse with a pinhole camera. CAMERA OBSCURA - Is a box used for sketching large objects? The term means dark chamber. The box contains a mirror set at 45-degree angle. Mounted in the front end of the box is a double convex lens like that in a photographic camera. Light from the object or scene is transmitted through the lens. The mirror reflects this light upward to ground glass screen on the top of the box. There the light forms an image of the object or scene that can be sketched easily. FIXED FOCUS CAMERA - The most basic of all camera, have a non-adjustable lens. Most models have a single diaphragm setting and only one or two shutter speeds. Most fixed focus cameras, including many inexpensive, pocket-sized models, use 110 or 126 size film. The negative of such film require considerable enlargement, which may produce a fuzzy image. In general, a fixed focus camera can take satisfactory photographs in ordinary daylight but not in dim light, because its lens does not admit much light. The camera may produce a blurred picture is moving or less than two meters away. Many fix-focused cameras can take flash pictures. Disposable cameras are a kind of fixed - focus camera that combine a plastic lens, a shutter, a film in one small box. The entire camera is taken to the photo laboratory when the roll of film has been exposed. POINT AND SHOOT CAMERA - Have many automatic features that make them easy to use. Electronic devices inside the cameras automatically adjust the focus, set the light exposure and the shutter speed and advance and rewind the film. A built in electronic flash automatically supplies light when too little light reflects from the subject. The cameras are equipped with high quality lenses that produce a sharp image. Some of them have a zoom lens. Point and Shoot cameras use films that measure 35 mm. Since their introduction in 1970’s theses cameras have gained wide popularity among amateur’s photographers. SINGLE LENS REFLEX CAMERAS - Appealed to skilled amateur photographers and to professional photographers. The camera’s name refers to its viewing system. The photographer views the subject through the camera lens rather than through a separate viewing lens. A mirror between the lens and the film reflects the image onto a viewing screen. When the shutter release button is pressed to take a picture, the mirror lifts out of the way to allow the light to expose the film. Thus the photographer sees almost the exact image that is recorded on the film.