Some people have what is called eidetic imagery or “photographic memory.” Visual perception is retained as vivid images that are so sharp that they can be scanned and described in detail. Very few persons have eidetic imagery. It seems to be much more common in children than in adults. Persons said to have photographic memory are much more likely to be relying on ordinary visual memory than on eidetic imagery.
Hypermnesia is the exaggerated recall of details of experiences long past. It may occur when a person is under extreme tension, as when in sudden danger. Amnesia is partial or complete loss of memory. It is usually caused by brain damage or by emotional disturbances.