Your self-description sounds entirely typical to me. I don’t think most people can imagine detailed photographic images (e.g. of faces), though there do seem to be some who can, like certain autistic savants.

It seems likely that people’s external verbalizations of their internal experience vary widely enough that it’s difficult or even impossible to gain a useful understanding of that experience from survey answers. Sort of like when people claim non-human mammals have no consciousness or sentience because they don’t talk.

For example, just because the picture-book illustrator profiled in this article has a “vivid imagination” doesn’t mean she can literally visualize a full-fidelity photographic mental image of a whole book spread. As a photographer, when I see a scene I can “previsualize” what kind of picture I might get after fully editing/printing the image days later. But that just means I can conceptualize particular visual effects, think about the lighting, texture, contrasts, colors, and put them together in an abstract thought, not that I can precisely “see” the picture exactly as if it were finished in front of me. I would say I have a “vivid imagination” for photographs, but my mental experience of remembered or imagined vision is probably pretty similar to yours.

What about people who complain about how a character looks in a movie adaptation of a book? I never see characters in a book so the movie can do whatever they want as far as I care. But other people get quite indignant over this. Can anyone here attest to what level of imagination one has to do that? I strongly suspect you're over generalizing from your own experiences, this might be a way to test it.

Maybe it's difficult to judge because people don't usually talk about it. I'd say I can visualize things just as vividly as I would experience when I look at them. That is, I won't notice every detail, but I don't notice every detail even when I'm staring right at something. I can look at something, look away for a while and visualize it, then look back at it and compare the subjective experience, and it's pretty much the same. It's more along the lines of getting the same mental stimulation of recognition and experience as I would get if I were looking at something, and it's the same as other senses. I can imagine myself on a beach, see the contrast of colors of leaves and the sky, hear the waves, feel the courseness of the sand, smell the sea, and I know from experience that if I were actually there, I would have the same sensations except I couldn't turn them off easily.

See, descriptions like this make me think that many people do indeed see clearer mental pictures than I (grandparent post) do. I'm going to have to do some informal surveys of friends and family!

It's just that we have predefined looks for a given type of characterization that sometimes adaptations don't get quite right. With time I've gotten over the fact that yes, a character from an adaptation probably will look different from what I imagined and I expect it as a normal thing.

Think of it as personal stereotypes. For example I often imagine how a character looks before getting to the physical description and in that case it's very hard to change my predefined image. Even if e.g. the description says it's a tall blonde character with a big nose if I had already imagined the character small and with black hair I can't change that throughout the book. I've actually tried to and it's very hard. If I concentrate I'll get the correct image out but next time I'll encounter the character I will automatically think of the previous picture.

Personally I think this is pretty regular and other people are like that too, but how can I be sure?

Its a useful technique, to never describe your protagonist in a book. Allows the reader to customize, imagine themselves in the role, to really identify. I know 'Twilight' is famous for Bella's blank aspect. Also an old childrens' book "Harris and me" had a main character that not only was never described; they never had a name.