8 hours
16 hours
24 hours
Several days
Correct Answer: Several days

A little background…

French inventor Joseph-Nicéphore Niépce is credited with making the first permanent photograph in 1826 using a camera obscura and a pewter plate coated with bitumen of Judea (an asphalt derived from petroleum) that was exposed then washed with lavender oil and petroleum to remove the bitumen not hardened by light, achieving the image above.

The amount of time that it was exposed is disputed, however. It was long suggested that the exposure time was 8-9 hours, however, researchers dedicated to preserving the history of photography studied Niépce's notes and have since reported that it would have in fact taken several days of exposure to capture the image.

Choose your answer. The correct choice and a brief explanation will show below. Content is intentionally upside down, so there’s no peeking before you answer.