I don't think I have a very difficult time visualizing things, but I seem to have a hard time describing what people look like. Whenever anyone asks what person X looks like, I always really struggle with the question and rarely give a useful answer beyond things like skin color, hair color, and sometimes height. I don't know why this is at all -- whether my visual memories (maybe of specific people?) are missing fine details, whether I'm just generally lacking in practice in describing people's appearance in words, whether I'm especially inattentive to people's appearance, whether it's a psychological block, or something else. (I don't experience face blindness; I can easily recognize and distinguish people when I see them in person.)