In Italian, the term camera obscura means "dark chamber." By Brady's time, it was a light-tight box with a small opening in one side and a frosted glass panel on the opposite side. This construction is based on a principle of optics that was known to ancient civilizations and described by Leonardo da Vinci in the fifteenth century. When light entered the dark chamber through a tiny opening, the beam projected an image of the view outside onto the surface where the light fell. Special rooms were designed to display this magical phenomenon, which enabled audiences inside to see a luminous image of the world outside. In the sixteenth century, Italian artists added refinements, shrinking the large chamber to a portable box and replacing the pinhole opening with a lens. This tool became popular with many artists, including the Dutch painter Jan who reproduced the glowing effects of the camera obscuražs image in his canvases. Tourists also enjoyed using the camera obscura to observe scenery while they traveled.