During the English Google SEO Office-Hours From November 5, 2021, John Mueller addressed a question about images. The video below is queued to the spot where he read the question.
I’ve edited the scenario this person described:
“I have portfolio-style sites with pages each showing 10 to 30 thumbnails displayed in a gallery and in full size when clicked.
“Do you advise in on considering each image having its own page and listing it in a sitemap, or should I canonicalize them all to the main kitchen page and list only kitchen in the sitemap, as in reality there's only one HTML page there?”
John’s response, which I’ve edited for clarity, was:
“But essentially, the aspect of having a unique image landing page is something that really helps when it comes to image search, because otherwise, if we just have this portfolio page with 30 small thumbnails on it, and someone was searching for an image, it's hard for us to say, ‘Well, you'll find the information you need on this big landing page with lots of images on it,’ because chances are, the image is somewhere where they don't see it offhand, and they'd feel kind of confused if we sent them there after searching for that image.”
Do This (What’s Mentioned Above) If You Care About Image Search
“The thing with image search is that it works kind of separate from normal web search, and not all sites care about it. It's not the case that if you have good performance in image search, that you'll have better performance in web search.
“You can essentially treat these as separate things, and from that point of view, if you only care about web search--if you don't really need these images to be visible in image search--then this might not even be something that you need to care about, so I think those are kind of the different options there.”