How to write an image description | by Alex Chen | UX Collective

a "how-to guide ... through an online survey of Blind / low vision / visually impaired people."

Discovered via Mastodon, where the culture is not to boost any toot containing non-accessible images, but applicable to all online publishing.

"alt text and image descriptions are ... not actually the same thing. Alt text refers to the text specifically added to the alt attribute, and is often short and brief. Image descriptions can be found in the alt text, caption, or body of the webpage and are often more detailed...

... there is a storytelling aspect to writing descriptions... I came up with a framework that I recommend called object-action-context: The object is the main focus. The action describes what’s happening, usually what the object is doing. The context describes the surrounding environment..."

Example:

"Object: Black Lives Matter sign
Action: being held
Context: in a crowd"

This approach keeps the description:

• "objective so that people using the description can form their own opinions about what the image means.
• concise so that it doesn’t take too long for people to absorb
• descriptive enough that it describes all the essential aspects of the image."

Concise and descriptive are at odds, so "be as descriptive as your audience needs... If your work is highly visual and your audience is interested, then add more detail... Make sure to transcribe all the text... write hashtags in title case ".

There are plenty more examples in the post illustrating variations, right/wrongs, etc.