In their series ‘silent world’, paris-based, franco-german artistic duo lucie & simon use tricks of the photographic trade to render the world’s busiest cities free of cars and even people. Neutral density filters allow photographers to limit light entry without closing the aperture or increasing the shutter speed. the higher the F-stop reduction, the greater the effect, allowing for super-long exposures which make moving objects like people and cars essentially invisible, while only immobile structures remain. extremely high level filters are used by NASA to analyze star patterns. via
it’s even more amazing once you read up on how they managed to do it too.
Silent World by Lucie & Simon have captured some of the world’s most populated cities completely devoid of any human activity.