Topic 4.3: Descriptions and captions of graphics
Use of textual descriptions of images in digital documents is vital in ensuring the inclusion of people with visual difficulties. This helps to have information presented in a digital graphic, accessible to anyone who may not be able to physically see the visual format. This topic focuses on key concepts and the principles of describing and captioning graphics.
4.3.1 key concepts used in graphic descriptions
a. Accessibility: Accessibility can be viewed as the "ability to access" and benefit from some system or entity. This is about making things accessible to all people (whether they have a disability or not). It is the sense considered here refers to the design of products, devices, services, or environments so as to be usable by people with Disabilities. The concept of accessible design and practice of accessible development ensures both "direct access" (i.e. unassisted) and "indirect access" meaning compatibility with a person's assistive technology (for example, computer screen reader).
b. Captions: refers to the sentence or group of words that is written on or next to the picture to explain what is being shown. For visual impaired persons, these words should be written in Braille system.
4.3.2 Principles of Describing and captioning graphics.
It is important to ensure that images intended to convey any information to an audience in particular people with visual difficulties conform to key principles. The principles to consider while designing images include the following:
1. The purpose of describing images
An image description is used to convey the information contained in an image to a person who cannot access it in its original form. It is essential that blind and partially sighted users receive the same information as their sighted peers. Image description enables users to:
§ Achieve the learning outcome intended by the author
§ Participate in discussions based on the information within the image.
2. What counts as an image?
Images include graphs, charts, diagrams, photographs, illustrations and artworks. They also include mathematical equations, chemical formula, musical notation and special symbols, as a screen reader will not be able to access these to read them aloud.
Many blind and partially sighted readers use screen readers to access electronic materials on screen. Within an electronic document a screen reader will not be able to access an image, so will pass over it. If images on the web do not have alt text, again a screen reader will pass over it; likewise, in an audio or DAISY file, the information will be missed unless the image is mentioned in the text.
A person using magnification software to read printed material may struggle to see the details of an image and may only see a small part of an image at a time. An image overview will help them understand what is being shown.
Modified images such as large print and tactile diagrams will need the layout of the image and describing its parts before the information within the image can be understood.
3. Do all images need describing?
For practical purposes, the answer to this has to be 'no'. There are images which are decorative or summarize information in the text and a description would not add anything of use to a blind or partially sighted user. An image needs describing if:
§ It contains essential information which is not readily accessible anywhere else
§ There is data within an image that needs to be conveyed
§ There is data within an image which needs to be interpreted
§ It is an image used as a basis for discussion
§ It is a visual summary of a long section which has no text summary
§ It is decided that a caption is needed or the existing caption is not adequate
§ It introduces a type of diagram commonly used in the subject area
§ It is a modified graphic such as a large print image or tactile diagram
§ It has been removed from a transcribed version of a document, so this information is missing
§ It is being used to teach how to use a particular type of diagram.
For charts, graphs and diagrams where the image summarizes data and other essential information: it is this data and essential information that needs to be described.
For images where a subjective response is required, or if the image is teaching a visual discrimination skill, then the appearance of the image will need to be carefully described.
For modified large print images and tactile diagrams, it is crucial that the layout of the image is described before the features of the image. This will enable a user to understand what features are in the image and what it is showing.
If an image is purely decorative and adds nothing to the text, then a description may not be necessary; or depending on the context a short note for example 'photograph of John Smith' will help a reader who has a small amount of vision to decide whether to spend time studying it with a magnifier.
4. Who should write the description?
Ideally, the best person to write descriptions is the author of the material. The author knows the purpose of the image and its importance and can be satisfied that any descriptions contain the intended information.
However, within the publishing chain the author may not see the final image and within education a transcriber or support worker may need to describe existing materials. If this is the case, it is crucial they understand the original intention of the image.
5. What kind of description does the image need?
The level of information needed in a description will depend on the context of the image and how it is going to be used. Due to the extra time needed to read and understand an image, a description needs to be concise:
§ A single sentence listing the key features or trends may be sufficient.
§ Information from a graph can be effectively written as numerical data, or presented as a table.
§ Complex diagrams may need a description that is the equivalent of several pages of text.
6. Incorporating image descriptions into a document
You will need to consider where to incorporate a description, as it can be written into the main text or provided as an additional document.
It is important that images reference the original material, by including any page numbers, figure references and titles. If a separate document containing the image descriptions is provided, this can be in the recipient's preferred format; such as Braille, audio or large print.
Electronic materials: If authoring original material, a description can be written into the main text. Short descriptions can also be written into formatted captions or alternative (alt) text.
Audio materials: Depending on where images appear within the material, a description can be read after an image is first mentioned; or at the end of a chapter. It is important to mark the beginning and end points of an audio description to ensure a blind or partially sighted user can distinguish the original material from information given in addition. A separate audio file that references the images may need to be produced if there are many images and it is felt that descriptions will interrupt the flow of the text too much.
Presentations: Any images given within a presentation will need their data and other key information read aloud to the audience.
Business documents: Any documents containing images, charts and graphs containing data, can be summarized within the text after the image appears; or a separate document produced which references the images can be provided.
Published material: A separate document can be produced which contains the descriptions of the published images. Any references such as image titles, image references and page numbers will need to be included.
Accessible images: These are generally produced separately along with a description. This description may be in a braille, print or audio format to accompany the image.
Educational materials: If an author of a course is not able to write descriptions, they should at least give an indication of the type of description needed to save unnecessary work later. For example, a note could be attached to each diagram such as:
§ Adequately covered in the text or caption.
§ Needs a couple of sentences about trends on the graph.
§ understanding of this type of diagram is desirable for communicating with others in this field.
§ This diagram is too complex to describe adequately; students are recommended to consult their tutor.
A description can then be written and incorporated according to the format of the materials (UK Association for Accessible Formats, 2012)
