I found out recently that I have aphantasia, based on everything I've read. When you tell me to visualize, I imagine. I don't see it. An apple, I can imagine that. I can describe it in incomprehensibly sparse details. But when you ask details I have to fill them in.

I hadn't really placed those three dots in a specific place on the apple. But when you ask where they are, I'll decide to put them in a line on the apple. If you ask what color they are, I'll have to decide.

I'm pretty sure I don't have aphantasia. I don't see the apple either; it doesn't occupy any portion of my visual field and it doesn't feel similar to looking at an image of an apple. There's more of a ghostly, dreamlike image of an apple "somewhere else" whose details I only perceive when I think about them, and fade when I pay less attention. But the sensation of this apparition is a visual one; the apple will have an orientation, size, shape, and colour in the mental image, which are defined even if they're ghostly, inconsistent, and change as I reconsider what the apple should look like.

+1, spot on description of aphantasia.