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Electronic Image
Still-Digital  Cameras

Photography (Advanced) - Advanced manual for photography and other graphic techniques
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One  major  problem  you  will  encounter  when setting   up   an   electronic-imaging   station   is interconnecting the various components that make up the   imaging   system.   The   technology   in   each component area is developing at a rapid rate. With the ever-increasing  number  of  hardware  components  and software packages available on the market, setting up the links between the devices can become frustrating. Before choosing new components for a system, you must look carefully at each piece of new equipment to be sure it is compatible with the existing system. INPUT Several  ways  to  acquire  photographs  electronically are used. You can obtain these photographs from digital or  still-video  cameras,  or  you  can  scan  and  digitize existing film and paper images. Before a computer with the appropriate software can be used to modify or enhance an image, the image must be converted to digital values. Images that are imported  from  a  still-video  camera  are  in  analog waveform. An analog waveform is a value that varies continuously  over  time  (fig.  3-4).  For  an  analog waveform to become a digital signal, both the value and the time must be changed into noncontinuous, numeric values of ones and zeros (fig. 3-5).  The process used to determine time is called sampling. Sampling is done at equal increments of time. Conversion of continuous values into distinct values is called QUANTITIZING. The  combined  process  is  called  analog-to-digital conversion (A/D conversion) or DIGITIZING. The A/D conversion process is an approximation. When the sampling rate is low, a very inaccurate representation of the signal results. When the sampling rate is high, virtually an exact copy of the original signal is attained. When color images are digitized, the red, green, and blue information is handled as three separate sets of data to produce three sets of digital information. Figure 3-4.—Analog waveform. Figure   3-5.—Digital   signal. In this case, three A/D circuits are used and the encoding is  done  simultaneously. When an image is digitized, a series of points are created. These points are called pixels. When the resolution of the display system is low, the individual pixels  may  be  noticeable.  This  objectionable  resolution is  called  pixelation. Electronic  Still  Cameras The advantage of using a digital or still-video camera is the image may be captured and inputed to the electronic-imaging workstation instantly. The features on these cameras are basically the same, and they are used in the same manner as conventional cameras. The features  of  conventional  cameras  and  electronic cameras that are similar are as follows: The lenses may be fixed or interchangeable, depending  on  the  camera. The lenses are identified by f/stops and focal length. The focusing may be fixed, automatic, or manual,  depending  on  the  camera. The range of shutter speeds is similar. The flash may be built-in or have a dedicated hot shoe. Each electronic camera has an image sensor. The image sensor, called the “charge-coupled device” (CCD), is the main component of an electronic camera. The CCD is rated in size, pixels, and ISO. The larger the CCD, the more pixels it can record, thus the higher the resolution. However, the resolution quality and the exposure range of an electronic camera is not as great as what can be achieved with film. 3-8







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