illusion of seeing something

Right, while for the most parts I can clearly describe what I saw when I was LD-ing, I have noticed that in some instances, that could be attributed to dream instability or indeed the brain just being lazy/tired, is that I would look at things in a dream, sometimes it was an environment, sometimes an image, and the image would make sense in the dream but when I would wake up I'd recall just a few vague shapes, or a soup of colors of that image - at first I assumed that it was just my dream recall, but since overall I recall my LD's quite clearly I now think the brain 'saves power' by, instead of generating a real image just cheats and gives you some concept of an image/fools you into believing you are observing something- but when you wake up it's quite impossible to describe the image/scenery in question- at best a few colors or the general idea of what it was. I believe this not only me- I think many people mistake this for poor dream recall.