Digital imaging needs knowledge of a new language

We all know dealing with computers requires us to learn a new language. We talk about cpu's, hard drives, scanners and other terms which describe our computer systems.

The increasing interest in computer imaging has increased this new vocabulary. Now we talk about "jpeg's", "gif's", "tiff's", "png's" and other terms associated with our new digital images. What are these terms and what do they mean?

Let's start by looking at some very general terms. To make a computer actually do something requires computer "programs." People with specific goals write these programs. There are Word Processing programs that allow us to write documents; Spreadsheet programs for analyzing data; Database programs for collecting data; and the many new programs that allow us to manipulate images we get from our digital or video cameras and scanners.

Each of these programs has its own way of arranging data. This arrangement is called a "format." For instance, Microsoft Word has its own internal way of arranging its documents. When you save your letter to Aunt Helen, it is saved in a particular arrangement so that the computer recognizes it as a file that should be opened in Microsoft Word.

The way the computer recognizes a particular format is by the three letters appearing after the period (dot) in the file name. Thus, "aunthelen.doc" is recognized by the computer as a Microsoft Word "document" file because of the ".doc" in the file name.

How do formats come about? A very popular format in digital imaging is "jpg." Where did it come from?

In the 1980's, the International Standards Organization (ISO) formed a committee to study methods to make digital photographic images compatible with computers. This committee was named the "Joint Photographic Experts Group." It consisted of industry and scientific experts.

This group developed a computer "algorithm" that made digital image files smaller and easier to transfer from device to device. The term "algorithm" means a "method of solving a certain kind of problem," or "a way to get something done."

They named the format that uses this algorithm "jpeg" because they were the (J)oint (P)hotographic (E)xperts (G)roup. Since computers like three letter file "extensions," this became shortened to "jpg." Thus the "Jay-Peg" was born.

The "jpg" algorithm is known as a "lossy compression" algorithm. It takes a large digital image and compresses it to make it smaller. In doing so, some image data is lost. However, because so many digital images are displayed on computer screens, this loss is seldom noticeable.

So the "jpg" format with its lossy compression has become a standard in digital imaging.

In future columns we will discuss methods to manipulate this "Jay-Peg" format to accomplish particular image objectives.

Other image formats exist. There is the "TIFF" (Tagged Image File Format), "GIF" (Graphic Interchange Format), "PNG" (Portable Network Graphics), and many other very specific "formats" using their own "algorithms" to solve particular problems. Many digital cameras will internally convert images to these formats before being sent to the computer. Many computer programs will allow one format to be converted to another. Making these choices between formats will be discussed later.

If you would like to hear more about formats or other computer topics, visit "Coffee and Computers" at the Tustin Area Senior Center, 200 S. 'C' Street, any Friday morning starting at 9 a.m. Bring your questions or just come in and visit.

In the mean time, keep the neurons happy, synapses snapping and enjoy computing.


Dr. Art Holub is a long time resident of Tustin and teaches computer and Internet courses at the Tustin Area Senior Center and the Tustin Adult School. Visit his web site at: This column is written to address the computer adventures and concerns of older adults. If you have comments, questions or suggestions for future columns, Email HIM at:

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