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November 15, 2020

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By Nilakhi Banerjee

Camera obscura (meaning “dark room” in Latin) is a box-shaped device used as an aid for drawing or entertainment. Also referred to as a pinhole image, it lets light in through a small opening on one side and projects a reversed and inverted image on the other.

How It Works

As the name suggests, many historical camera obscura experiments were performed in dark rooms. The surroundings of the projected image have to be relatively dark for the image to be clear. The human eye works a lot like the camera obscura; both have an opening (pupil), a biconvex lens for refracting light, and a surface where the image is formed (retina).

Early camera obscura devices were large and often installed inside entire rooms or tents. Later, portable versions made from wooden boxes often had a lens instead of pinhole, allowing users to adjust the focus. Some camera obscura boxes also featured an angled mirror, allowing the image to be projected the right way up.

The History of Camera Obscura

The earliest written record of the camera obscura theory can be found in the studies of Chinese philosopher and the founder of Mohism, Mozi (470 to 390 BCE). He recorded that the image in a camera obscura is flipped upside down because light travels in straight lines from its source. During the 4th century, Greek philosopher Aristotle noticed that sunlight passing through gaps between leaves projects an image of an eclipsed sun on the ground. The phenomenon was also noted by 6th-century Greek architect Anthemius of Tralles who used a type of camera obscura in his experiments. During the 9th century, Arab philosopher, mathematician, physician, and musician Al-Kindi also experimented with light and a pinhole.

Familiar with these early studies, Leonardo da Vinci published the first clear description of the camera obscura in Cordes Atlantius (1502), a 12-volume bound set of his drawings and writings where he also talked about other inventions such as flying machines and musical instruments. He wrote (translated from Latin): “If the facade of a building, or a place, or a landscape is illuminated by the sun and a small hole is drilled in the wall of a room in a building facing this, which is not directly lighted by the sun,

Sun

Then all objects illuminated by the sun will send their images through this aperture and will appear, upside down. On the wall facing the hole. You will catch these pictures on a piece of white paper, which placed vertically in the room not far from that opening. And you will see all the above-mentioned objects on this paper in their natural shapes or colors, but they will appear smaller and upside down, on account of crossing of the rays at that aperture. If these pictures originate from a place which is illuminated by the sun, they will appear colored on the paper exactly as they are. The paper should be very thin and must be viewed from the back.”

Over the years, Da Vinci drew around 270 diagrams of camera obscura devices in his sketchbooks.

Daguerreotype

Niépce’s experiment led to a collaboration with Louis Daguerre. The result was the creation of the daguerreotype, a forerunner of modern film.

  • A copper plate was coated with silver and exposed to iodine vapor before it was exposed to light.
  • To create the image on the plate, the early daguerreotypes. Had to be exposed to light for up to 15 minutes.
  • The daguerreotype was very popular until it was replaced in the late 1850s by emulsion plates.

Emulsion Plates

Emulsion plates, or wet plates, were less expensive than daguerreotypes and required only two or three seconds of exposure time. This made them much more suited to portrait photographs, which was the most common use of photography at the time. Many photographs from the Civil War were produced on wet plates.

These wet plates used an emulsion process called the Collodion process, rather than a simple coating on the image plate. It was during this time that bellows were added to cameras to help with focusing.

Two common types of emulsion plates were the ambrotype and the tintype. Ambrotypes used a glass plate instead of the copper plate of the daguerreotypes. Tintypes used a tin plate. While these plates were much more sensitive to light, they had to be developed quickly. Photographers needed to have chemistry on hand and many traveled in wagons that doubled as a darkroom.

Dry Plates

In the 1870s, photography took another huge leap forward. Richard Maddox improved on a previous. Invention to make dry gelatine plates that were nearly equal to wet plates in speed and quality.