On the theme of image making and portraying memories, and the nature of memories as well, Tarkovsky says in his book "Sculpting in Time":
"We've come to the end of the day: let us say that in the course of the day something important has happened, something significant, that sort of thing that could be the inspiration for a film, that has the makings of a conflict of ideas that could become a picture. But How did this day imprint itself on our memory?
As something amorphous, vague, with no skeleton or schema. Like a cloud. And only the central event of that day has become concentrated, like a detailed report, lucid in meaning and clearly defined. Against the background of he rest of the day, that event stands out like a tree in the mist. (Of course he comparison is not quite exact, because what I've called mist and cloud are not homogeneous.) Isolated impressions of the day have set off impulses within us, evoked associations; objects and circumstances have stayed in our memory, but with no sharply defined contours, incomplete, apparently fortuitous. Can these impressions of life be conveyed through film? They undoubtedly can; indeed it is the especial virtue of cinema, as the most realistic of the arts, to be the means of such communication.
Of course such reproduction of real-life sensations is not an end in itself: but it can be given meaning aesthetically, and so become a medium for deep and serious thought.
To be faithful to life, intrinsically truthful, a work has for e to be at once an exact factual account and a true communication of feelings.
You were walking along the street and your eyes met those of someone who went past you. There was something startling in his look, it gave you a feeling of apprehension. He influenced you psychologically, put you in a certain frame of mind.
If all you do is reproduce the conditions of that meeting with mechanical accuracy, dressing the actors and choosing the spot for shooting with documentary precision, you still won't achieve the same sensation from the film sequence as you had from the meeting itself. For when you filmed the scene of the meeting you ignored the psychological factor, your own mental state which caused the stranger's look to affect you with particular emotion. And so for the stranger's look to startle the audience as it did you at the time, you have to prepare for it by building up a mood similar to your own at the moment of the actual meeting."