George Sperling was the psychologist who found that visual impression in iconic memory are photograph like in nature.
In Spreling's study during the 1960s, he conducted a study where he flashed a series of letters on a screen for 50 microseconds each for participants to recall. The results of his study revealed that participants perceived each letter as an iconic memory. That means after the participants saw each letter, the letters left a brief visual memory after it faded from the screen and was no longer in sight.