Leonardo’s Drawing Aid, the Camera Obscura

The CAMERA OBSCURA

The dictionary definition: 1) A darkened box with an aperture (convex lens) for projecting the image of the external scene onto a surface inside, based on the way our eyes see. It is important historically, because the concept lead to the development of photography once film was invented. 2) A small round building with a rotating angled mirror at the apex of the roof, projecting an image of the landscape onto a horizontal surface inside.

A small round building with a rotating angled mirror at the apex of the roof, projecting an image of the landscape onto a horizontal surface inside.

The Camera Obscura is based on the way our eyes function to see, with the same upside down image that our mind autocorrects to make us see everything right side up.

The first Eastman Kodak camera circa 1888

The word “camera” in Italian means ROOM, “Obscura” in means DARK. Thus Camera Obscura literally means a Dark Room.

A camera obscura is merely a dark box (or darkroom) with a very small hole in one wall that lets in light. Directly across from the hole the image from the outside world will be projected onto the surface, upside down. We are all familiar with a pinhole camera – the original camera obscura was basically a large room-sized version of that concept.

The reason the image is projected (upside down) is that light travels in a straight line, and when rays of light, reflected from a brightly sunlit subject pass through the small hole, the top rays go to the bottom of the opposite wall and the bottom rays go to the top of the opposite wall, thus it ends up as an upside-down image.

The camera obscura was one of the most interesting optical inventions Leonardo worked with. He was not the first person to use one of these, but he was first to notice the similarity between the way a camera obscura worked and the way the human eye functioned.

A camera obscura was a small hole in the wall of a room and the image would appear on the opposite wall, upside down. The reason this happens is that light travels in a straight line, but when some of the rays reflected from a bright subject pass through a small hole, they become distorted and end up as an upside-down image. Imagine trying to squeeze an object into a space that is too small for it.

Leonardo thought of the human eye as the most important organ in the body. In his diary, he wrote, “This is the eye, the chief and leader of all others,” and used up hundreds of pages jotting down ideas about how the eye functioned.

He went so far as to dissect human eyes to study them. He used his observations to develop a projector, bifocals, and even came up with the idea for contact lenses – even though he never actually made them.

Leonardo also conceived of a gigantic lens to harness solar energy for the dyeing and tanning industry. Today, historians even believe that he came up with the idea of a telescope long before Hans Lippershey, the Dutchman who is credited with inventing the telescope in 1608.

Leonardo wrote, “…in order to observe the nature of the planets, open the roof and bring the image of a single planet onto the base of a concave mirror. The image of the planet reflected by the base will show the surface of the planet much magnified.”