Two persons receiving the same ocular impression see a different picture. One perceives the world according to inner laws, regardless of the fact that the object itself is a constant quantity, according to Kant. Vision is biased. One person sees something that escapes another's attention.
I long ago found out that visual memory has specific qualities. Although I am a practicing physician, I have found it hard to remember faces of my patients, but whenever I meet them in the street I am able to identify them at a distance by their movements.
A surgeon admitted that he was never able to identify his patients by their faces but only by the cicatrix left by the incision.
One overlooks many impressions if one is inwardly distracted from the outer world. Although I am interested in architecture, I have overlooked buildings in Vienna in a neighborhood which I have traversed