Monday, August 19, 2019
Graphics :: essays research papers
5.2 Images: Information without Words or Numbers Images play a fundamental role in the representation, storage, and transmission of important information throughout our professional and personal lives. In many professions, including publishing, art, film making, architecture, and medicine, it is crucial to be able to represent and manipulate information in image form. Furthermore, with the development of multimedia technology and virtual reality, many other professions are beginning to explore the power of representing information in visual form. In Chapter 3, we introduced the ideas behind binary representation of information, and in particular showed how integr and text can be converted into binary form. We also mentioned that other types of information can be represented by bits, and briefly described the process one might use to convert an image into binary digits. We then suggested how this would extend to representation of time-varying imagery, or video. 5.3 Cameras and Image Formation As mentioned in the introduction to this book, the film-based camera is over 150 years old. Recent advances have provided a variety of alternatives to the use of conventional film, but the basic image formation process has not changed. This process may be familiar to you from experience with basic optics, and is illustrated in Figure 5.1. The essential components of this system are: the object or scene to be imaged, the lens, and the image recording medium (retina of the eye, film, or other device). The image recording medium is usually located in a plane parallel to the lens, known as the image plane. Note that the image that is formed is inverted; this is usually of no consequence because the display device may easily correct this condition. The resulting image represents a projection from the three-dimensional object world to the two-dimensional image world. The focal length specifies the distance from the lens to the image plane. More useful to us, it also indicates the degree of magnification of the lens. From 35 mm photography, we know that a lens of 50 mm focal length is considered ``normal'' (in the sense that the resulting photo will contain the same expanse of image that a human would see from the same point as the camera); one of 28 mm focal length is ``wide angle,'' and one of 135 mm focal length is ``telephoto.'' For a different film (image) size,those focal lengths would change, but the principle remains the same.