If I have a photo gallery where each photo in the gallery has a mini-feed of 'related photos', should the alt text of these related photos describe these related photos or should they describe the fact that they are something like "a link to a related photo"?
As the title states I am asking my question in terms of SEO.
According to MOZ, alt text describes an image for bots and the visually impaired:
If you can close your eyes, have someone read the alt text to you, and imagine a reasonably accurate version of the image, you're on the right track.
So your alt text should be reasonably consistent, and should always describe the image itself. No need to include info like "related image" in the alt text. Instead, use an h- element to introduce that section of the page to average users and visually impaired users alike.
Alt attributes are for users, not search engines. If you're purposely writing alt attributes for search engines then you are providing non-natural alt attributes which, in turn, lowers user experience and sends bad signals to Google/Bing, search engines want content optimised for users, not search engines. Look after your users and the search engines will look after you.
Good usage of the ALT attribute is composing the image ALT value that consists of a short description that informs users the context of the image. Sometimes describing less is often more and other times more is more! Your descriptions should contain the elements of the image that you want them to visualise, it is not for telling Google to rank THIS because of this KEYWORD. Treat the ALT tag as a solution for partially impaired, completely impaired or for users that have disabled images in their browsers.
