Describing images is an art form.
Most people know that images need alternate text (alt txt) to describe what is displayed. There are many layers to be included.
First, the summary “alt text” provides information for a screen reader user to know about the image, and to determine if the image is important. Trying to put that into 125 or so characters can be challenging. While that gives a bit of information about the image, it may not be enough to provide the meaning of that image. And unless that information is in the body of the text, a sighted user using text to speech software will not know it exists.
The “alt text” has to relate first and foremost to the learning objectives for the course content. Many images are placed in text to enhance comprehension. The image may have accompanying text that goes with the image, such as labels or a key. Simply listing the labels in the alternate description is not enough. Unless the alternate description gives enough information to form a picture of the image “in your mind’s eye”, it is not enough for content mastery. An additional text description may need to be added to an image to provide additional information regarding what is represented.
If it is important content that will be tested for mastery, it will be important to think about how the alternate description can be turned around to determine if the student understood the material. It might be a bit tricky, especially if using the image with a description will need to be selected as the correct answer. If multiple images are used for answers, then each one will need a description to determine if the student mastered the learning objective.
Creating a link to another document that includes a longer description is another option, in order to provide enough information without adding to the text presented. A link back to the original document will provide the user with a way to navigate back to the original content. Adding additional references and materials to increase mastery of content will benefit all users.
In the previous blog post, text to speech and screen reading differences were outlined. A text description will allow the use of both tools in order to provide more information about the image. This follows Universal Design, in that adding additional descriptions of images can enhance the use of the content for all students, regardless of the tools they use.
But how do I know what to describe and how to describe it?
The DIAGRAM Center has given several tools that can assist in describing images.
The Accessible Image Sample Book created by the DIAGRAM Content Working Group is a free, online resource that shows many examples for creating accessible versions of digital images. The book is available in both EPUB and HTML formats. It is simply a guide for creating alternate descriptions.
It includes several different image examples to assist in the decision making process. Pick an image and follow the prompts. At the end of the process, there will be comments from the experts that will provide guidelines for creating accessible images based on the type chosen.
Another good resource is available from the National Center for Accessible Media at WGBH in Boston. “Effective Practices for Description of Science Content within Digital Talking Books” gives specific examples of images and how they can be created accessibly. Actual examples are shown in multiple formats that include charts, lists and graphs. The site also includes other information related to accessible images.
Using the resources will help in getting started when describing images, and also when reviewing other files for accessibility. Share your descriptions if you have content that others may want to use. Test the description by turning off your monitor and using text to speech or screen reading software to listen to your description. Do you get an accurate picture in your mind of what the essential content is? Could you pass the mastery test? If the answer is yes, in your mind, then try it out with students and get their feedback.