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In order to produce a reasonably clear projected image, the aperture has to be about 1/100th the distance to the screen, or less.
Many camerae obscurae use a lens rather than a pinhole (as in a pinhole camera) because it allows a larger aperture, giving a usable brightness while maintaining focus.
The earliest known written record of the camera obscura is to be found in Chinese writings called Mozi and dated to the 4th century BCE, traditionally ascribed to and named for Mozi (circa 470 BCE-circa 391 BCE), a Han Chinese philosopher and the founder of Mohist School of Logic.
In these writings it is explained how the inverted image in a "collecting-point" or "treasure house" is inverted by an intersecting point (a pinhole) that collected the (rays of) light.
The term "camera obscura" also refers to constructions or devices that make use of the principle within a box, tent or room.
Camerae obscurae with a lens in the opening have been used since the second half of the 16th century and became popular as an aid for drawing and painting.
The camera obscura box was developed further into the photographic camera in the first half of the 19th century when camera obscura boxes were used to expose light-sensitive materials to the projected image.
Light from an external scene passes through the hole and strikes a surface inside, where the scene is reproduced, inverted (thus upside-down) and reversed (left to right), but with color and perspective preserved.
The image can be projected onto paper, and can then be traced to produce a highly accurate representation.