I tend to build my imagination, so basically start at 5 and end at 2. I can't seem to get a perfect 1 without deliberate concentration, or day dreaming, where as most of my quick thoughts end at 2, as I don't see the worth in furthering the imagery. Faces though are beyond me, they are always blurred out, maybe a 4, even in my dreams. I'll know who the person is just by 'presence' or other means. It's like my mind purposefully looks away from the face, but I challenge myself to sculpt it into existence. I think this is why people need to take more art lessons, or learn it for themselves, as the older I get, and the more I learn to address artistic concepts, the more vivid my imagination has become, I know that faces will deblur themselves in time as I continue my practice. I truly think that the brain is a muscle, and many people forget that art is helpful to themselves, hence why some other comments I've seen on this thread have noted Mathmetitions tend to have lack of imagery. It uses a different part of your brain, than the logical, mathematical part does.