So, wait, are people normally actually seeing images, with their eyes, when they imagine what something looks like? Like, the brown-blackness of the back of your eyelids gets replaced with something you actually see, like it's projected there? I can imagine what something looks like, and I guess I sort of 'see' it, but closing my eyes doesn't make it any more real. It doesn't seem to involve the eyes or any part of t…
Most people are like this, with variation in the degree of vividness and control. Some people can make realistic detailed scenes, for other people it's harder and their images are often blotchy or lacking in detail and colour. I'm in the latter group.
If you don't have any of this at all and you're surprised by the whole idea, you are probably aphantasic.