Choosing the Best Graphic Format for the Job in Office

If you've ever wondered why the formats of graphics on the Web are different from those used in documents, presentations, or spreadsheets, you're not alone. With TIFFs, GIFS, BMPs, and PNGs, it's hard to know which format to use and with which program to use it. Knowing what formats are out there, and learning about the advantages and disadvantages of each can help you create lively documents, presentations, and Web pages.

Popular raster graphic formats

BMP (bitmap), GIF (Graphics Interchange Format), JPEG (Joint Photographic Experts Group), PNG (Portable Network Graphics), and TIFF (Tagged Image File Format) are raster image formats. A raster image is also known as a bitmap and is created from rows of small dots called pixels ("picture elements") or "bits." Because a raster format uses a fixed method of specifying an image, the image cannot always be immediately rescaled without losing definition.

Bitmap (BMP)

The Microsoft Windows® BMP format (.bmp file extension) can display millions of colors. Because it is supported by several programs, it is an extremely practical file format to use when you are providing an image to someone who may not have the program in which you created the image.

Graphics Interchange Format (GIF)

The GIF format (.gif file extension) is one of the two most common file formats for images on the World Wide Web, since it is supported by almost all Web browsers. Because this format can only display a maximum of 256 colors, it is best used for black-and-white line drawings, color clip art, and pictures with large blocks of solid colors. The GIF89a format also supports both transparency and animation. Use GIF files for:

• Images that contain transparent areas.
• A limited number of colors, such as 256 or less.
• Colors in discrete areas.
• Black and white images.
• A small-size image, such as a button on a site.
• Images in which sharpness and edge clarity are important, such as line drawings or cartoons.
• Images containing text.
• Animations.

Joint Photographic Experts Group (JPEG)

The JPEG format (.jpg or .jpeg file extension) is the other most common file format for images on the Web. It is not limited to 256 colors, so you can use it to display high-quality photographs, or pictures containing millions of colors. Because it is designed as an image storage format, it can efficiently compress large, high-quality photos into very compact files, so it is very useful when you want to send a large image in e-mail. However, the more you reduce your image's file size (or modify and re-save the image), the more image information is discarded — and quality is decreased. Moreover, this format does not support transparency or animation. Use JPEG files for:

• Photographs.
• Natural-looking images.
• A large number of colors, such as in the millions.
• A great deal of detail, such as a photograph of a house on a real estate site.
• An image with large dimensions.

Portable Network Graphics (PNG)

The PNG format (.png file extension) can display millions of colors. Because it is such a new format, however, fewer browsers currently support it (although it is quickly gaining support). Images saved in this format will not degrade in quality, even if the file is compressed. It supports transparency, but it does not support animation, since it cannot contain multiple images.

Tagged Image File Format (TIFF)

The TIFF format (.tif or .tiff file extension) produces very high quality images and is therefore used in publishing quite often. It can display millions of colors (although grayscale images are limited to 256 colors or shades), and typically results in larger image files than the GIF or JPEG formats. If you plan to edit an image in a program other than the one in which you created it, saving it in this format is helpful, since it is widely recognized by various programs.

The most common graphic file formats that Office supports

Note: Depending upon the program you're using, you'll need a graphics filter installed to insert any other graphic file formats. If you didn't install the filter when you installed Office or your specific Office program, you can run the setup program again and add the graphics filter. For more information about graphics filters, see Help for your particular program.

Figure out the best file format for your task

When you save your document, data and workbooks, or presentation as a Web page in Hypertext Markup Language (HTML) format, all graphics (including drawing objects and pictures) are saved in GIF, JPEG, or PNG format so that they can be viewed in a Web browser.

If you reopen the Web page in Word, Excel, or PowerPoint, the graphics will be in their original file formats so that you can still edit them as you normally would.