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To illustrate the use of the Camera Access program and how its use can result in potential storage and transmission problems, lets save an image using several file formats. Exhibits 5 and 6 illustrate the Camera Access program options for saving images when using the JPEG and TIFF file format options.
In examining Exhibit 5 note that the program uses a dialog box with a slider whose quality value is shown set to 90. By adjusting the quality bar down to 75, you can substantially decrease the storage requirements for the image of the house without any visual degradation becoming noticeable. For example, a quality value of 90 resulted in the image having a data storage requirement of 236,718 bytes. When the quality value was set to 75, the data storage requirement of the image was reduced to 41,272 bytes, or approximately one-sixth of the storage resulting from the use of a 90 percent quality factor. Thus, perhaps the first lesson that deserves mentioning when storing images obtained from the use of a digital camera in a JPEG file format is to consider reducing the quality value from its default value of 90 on some programs and high used with other programs.
Based upon a lengthy experimentation process performed by this author on images of homes, persons, and household objects, it was determined that a quality setting of 75 or medium as used with some programs will result in a level of clarity that is essentially indistinguishable from the highest JPEG quality setting while reducing storage requirements by approximately a factor of six. Since data transmission time is proportional to data storage requirements, this means the image will require one-sixth the transmission duration when stored using a quality value of 75.
Exhibit 5. Controlling Storage Requirements of an Image Using JPEG.
Thus, the use of a large number of frequently accessed JPEG images, such as on a frequently accessed Web site, using a well-thought out quality value can significantly reduce the transmission requirements on a network. If your organization is using an Internet connection where the service provider bills based upon the average occupancy of the connection, the reduction in storage and transmission time will also result in a reduction in your organizations monthly Internet access bill. Thus, an appropriate JPEG quality value setting can provide a variety of network related benefits. Now that we have an appreciation for handling images stored in JPEG, lets turn our attention to TIFF.
Exhibit 6 illustrates the two options supported by the Minolta Camera Access program for the storage of images using the TIFF file format. In examining Exhibit 6 you will note that the program supports No compression and PackBits storage. Although your first inclination might be to select the PackBits option as it represents a form of compression, depending upon the composition of the image that selection can actually result in an expansion of the storage requirements of the image. This is because PackBits is a lossless compression method that looks for repeating sequences of bits and encodes them using a code to define the occurrence of compression, a byte indicating the group of 8 bits that are repeated, and a third byte that represents a count of the repeating bytes. When an image has frequent occurrences of small variances in its background, such as the lawn shown in the photograph of the home, the use of PackBits compression will result in an expansion of storage. For example, the image of the home required 948,506 bytes of storage when the TIFF PackBits compression method was used. In comparison, 942,996 bytes of storage was required when the image was stored in TIFF format without compression.
Exhibit 6. Using the TIFF Packbits Compression Method on an Image.
It is important to note that there are six storage formats specified under the TIFF file format. Those not supported by the Camera Access program include G3 and G4 fax compression methods, Lempel Ziv Welch (LZW) lossless compression and JPEG lossy compression. Thus, to efficiently store an image using the TIFF file format requires the use of a third party image manipulation program such as Adobe Corporations PhotoShop. Thus, two additional items that warrant concern when using a digital camera include carefully considering the options supported by a programs file storage option and the details of an image. If the software provided with a digital camera does not support certain file formats or options associated with certain formats, you should consider the use of a third party product to convert the image to a more appropriate file format. If an image has a considerable amount of small detail, certain compression methods can result in expansion of the size of the file.
The best method you can use to consider the effect of images upon network performance is experimentation. That is, if you are considering using JPEG you should first consider storing an image using a sequence of different quality values to select an optimum value that balances storage and view-ability. If youre using TIFF you may wish to consider the use of a third party product that supports the full range of TIFF file storage options. Similarly, if you require a file format that is not directly supported by a program bundled with a digital camera, you should also consider the use of a third party program. Since certain images such as those placed on a Web server may be downloaded thousands of times per day, carefully considering the conversion of images into an effective file format can result in a significant reduction in transmission. This in turn can alleviate a costly network upgrade as well as reduce the cost of Internet access to corporate Web sites that are billed on a usage basis. Thus, the effective use of digital camera images can alleviate network bandwidth problems as well as potentially reduce the cost of communications.
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