I do have aphantasia, and until reading about it a couple of years ago I had no idea most people meant it literally when they talked about seeing things in their mind outside of dreams.
I can describe things in detail based on spatial relationships very accurately with my eyes closed, but at the very most I sometimes see vague subsecond flashes.
we're really lacking in ability to effectively describe the qualia of "imagining" - it could be that some people visualize internal fidelity more closely matching the raw signal of their optic nerve and others have an entirely separate way of experiencing. for myself I can say that I mentally visualize just fine but it is nothing at all like actual vision. if you asked me how is it different then this is where words fail. it's entirely different but I can't describe how.
It's weird. I can construct objects and run physics experiments in my head (not on Tesla's level), and it's a clear tactile sense to me, textures included. I can also play familiar tunes (in my youth this included symphonies, simplified into sections and solos) and mix flavors in my head. But the weirdest part is, I can hardly see a thing in there.
My inner imagination pales in comparison to the visualizations I experience on LSD. This experience sets up a nice contrast of what my mind is capable of VS what I generally am able to do when imagining.
I'm eager to try spending time imagining / visualizing things as I used to do when I was a kid, but it's hard to find time with all the exciting projects and busy life stuff in the way.
I can describe things in detail based on spatial relationships very accurately with my eyes closed, but at the very most I sometimes see vague subsecond flashes.