What Is It?
An image is converted into dots called "picture elements," or "pixels." The pixels are stored in computer files using "binary digits" or "bits"—long strings of 1s and 0s that don't look anything like your grandmother.

Just as with other important things in life (like ice cream), there are several flavors of graphic file formats for storing images. If your picture is black and white, it takes one bit to store one pixel. If your picture is "true color," it takes 24 bits to store one pixel.

Some formats are "lossless," meaning that you can copy them as much as you like and you won't lose any data. Others are "lossy," and the more times you copy the picture using them, the more you will degrade the image. Typically, you will want to save "master" copies of pictures in a lossless format, and you'll want to use a lossy format for e-mail and the Web.

Since image files can be large, some formats include "data compression" features so that they make smaller files than those that don't compress the data. It's important not to confuse loss and compression because they are altogether entirely different things. Due to compression, files of the same image in different formats will have widely different sizes—which means it takes widely different amounts of time to display them on Web sites or to send and receive them as e-mails.

You can learn a great deal about this subject by browsing the links included below.

Name Two of Them
Some of you may be surprised, but I won't be discussing the BMP and PCX formats in as much detail. They are only used on Windows platforms, and in my opinion, the others will do the job. Here's a partial list of formats:

BMP - Bitmap ("bee-em-pee"). Windows requires it for desktop wallpaper in older versions. That is the only reason to ever use one. Not used on Mac.

PCX - PC file format ("pee-see-eks"). Not used on Mac.

JPG - Joint Photographic Experts Group ("jay-pee-gee" or "jay-peg"). This makes the smallest files, so it's good for copies of your master. Generally best for Web photos.

GIF - Graphics Interchange Format ("jiff"). This makes the second-smallest files. Generally best for Web artwork or images with less than 16 colors.

TIFF - Tagged Image File Format ("tiff"). The most widely supported format, this makes the biggest files (unless you ask for compression, and that method varies from program to program). Macs can read this.

PNG - Portable Network Graphics ("ping"). A growing format for art, but not all browsers recognize it.

When It Works, What Does It Do?
The picture looks good! Actually, when it works, you get the best balance of image quality, disk space usage, and waiting time (if it's on a Web site or in an e-mail). Typically, for e-mails and Web sites, use JPG for photos and GIF for logos, artwork, or other images containing 16 colors or less. For a "master" copy, choose between TIFF and PNG based on what your software can do and on which one you like best. Both are "lossless" formats.

What's the Downside?
The downsides are issues of size, and of loss. By loss, I specifically mean that if you take an image and copy it to a JPG or GIF format repeatedly, you will eventually see that the image quality suffers.

How Do I Know If It's Not Working?

• Sometimes a lossy format, when copied, will result in a corrupted image.
  
• Sometimes a non-compressed format will create a really long e- mail or Web download.

One of the things that frustrates me the most is to find that the particular program I'm using either can't read or can't write in the format I prefer, so look at your choices under "Save As" to be sure you know what you can do.

What If I Change Computers?
Save the receipt.

What's the Genealogy Tie-in?
Making computer images of photos and documents is a constant occupation for genealogists. Putting together a scrapbook of images of ancestors is a great thrill.

Link Me Up (More stars is better)

• Scantips ****
  Just like its name suggests, this site has lots of scanning tips, including a method for getting the best pictures. It also has some great info about formats, file sizes, and strong and weak points. Examples of how the appearance of each format differs are blown up so you can tell.

• PCS Manual to Graphic File Formats **
  Not very pretty to look at (it could be as much as two years old), but this site has some detailed information about a large number of formats.

• UseNet Graphics File Formats FAQ ***
  This is aimed at experienced computer users, but it has some good information about converting from one format to another. Besides, these questions are frequent!

• About.com Graphics File Info ***
  This site has some rather involved info about vector and bitmap graphics, so if you want to know a lot more about computer graphics, visit it. It includes a GIF-JPG comparison.

What Else?
PDF files are technically graphic images, but they almost never get listed as graphic file formats. Some graphics programs will save in this format, but typically you have to buy an Adobe Acrobat Writer to make them.

Next time: Using spreadsheets for family history.

Beau Sharbrough is the president of GENTECH, the founder of the GENTECH and FGS Web sites, and a founder of the Lexicon Working Group. He would like to hear from you at beau@sharbrough.net, but due to the volume of e-mail received, he is unable to answer every e-mail message received. Please note that he cannot assist you with your individual computer problems. Visit Beau's Web site for information about speaking engagements. Beau is the father of two college-age girls and is another insufferable graduate of Texas A&M University.