I am the same with faces, but I have the same problem with everything I imagine. It's as though I can imagine things, but only in the same way you can look at a photo for 1/5th of a second. You get the general concept but no details.

I doubt I am special in this regard, but perhaps just on the lower end of the spectrum for normal. I cannot draw to save my life because I can't usefully imagine it in my head before it goes on paper.