For myself, I find I can create incredibly vivid images and scenes in my head up until the point where I consciously think about them being in my head, at which

For myself, I find I can create incredibly vivid images and scenes in my head up until the point where I consciously think about them being in my head, at which point they start to degrade and I can't really build them up again until I immerse myself in it again. This makes it really hard to perform the test of how vividly can you imagine something in your head (an apple is the usual one), because if I try to imagine it, at best it comes off as very poorly formed and hard to get a good focus on. But I know and remember much more clear scenes from times where I've been focussing more so on the scene than trying to imagine the scene, if that makes any sense.