Compared to printed images, Web images are easy to prepare and can be used without cost. However, there are drawbacks to using images on the Web. Image files are often larger than text files and take more time to download. Images command attention and can be distracting. When images are used to convey important information, people who cannot see them miss the message.
Images are not bad per se. Some concepts are easier to grasp when images are used to reinforce the text. For example, when assembly instructions include graphic depictions of each step, we have a way to visually confirm that we are on the right track. When product information includes a photograph, we know far more about the product than we would by simply reading a text description (Figure 4.1).
Figure 4.1: The Shopzilla site provides shoppers with a product image along with a text description. The image communicates information about the visual attributes of the product. www.shopzilla.com
However, images affect accessibility when they are used as the sole means of conveying information. When content is presented as an image, people who cannot see images cannot access the content. People who have viewing requirements may not be able to modify images sufficiently to meet their needs. People with technical limitations—such as low bandwidth or older browser software—may not have access to images.
In some circumstances, images can be used without concern for those who cannot access them. Images are effective for establishing a visual site identity. Images and icons that reinforce text are not always essential to nonvisual users. To achieve universal usability, we do not have to abandon images—indeed, doing so would make the Web difficult for people who are helped by images. We simply need to use images appropriately, and in a way that does not result in the exclusion of some users.