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Choosing Image File Formats

Before you can properly optimize your images, it helps to have at least a basic understanding of image file formats. Saving images in the wrong file formats can affect the quality of the image. It can also lead to much longer download times than necessary.

I almost always publish photographs to the web using the JPG file format. This file format is usually best for images that use more than 256 colors, which will include most photos.

Computer generated images, such as clipart, can almost always be saved as a GIF, substantially reducing the file size of most graphics, as compared to a JPG file. Exceptions to this would be some graphics using far more than 256 colors to create the image. At this time I feel that the GIF file format is still the best format for graphics which include transparent areas, as there will be no concern that the file will be compatible in all browsers.

When I am working with graphics which include 256 colors or less, and no transparent areas, I much prefer the quality return by using the PNG format. Usually I find that the PNG file will compress better for graphics and require less download time.

This is not to say that you cannot use the PNG file format for graphics with transparent areas, but in some browsers it may require some extra work that can extend beyond the skill level of the basic user. The PNG file format is not used for animated images.

It is really easy to check how many colors are included in an image using Paint Shop Pro X. From the menu, simply select: Image > Count Image Colors. A little box will pop up stating the number of colors used.

See Screen Shot

This tutorial is only intended to give a very basic understanding of choosing image file formats.
 

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J. Cricket Walker

Small Business Marketing Consultant and Scenic Photographer
Copyright © 2006 J. Cricket Walker of Online Photography Magazine All Rights Reserved


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