The history of the camera began even before the introduction of photography. Cameras evolved from the camera obscura through many generations of photographic technologydaguerreotypes, calotypes, dry plates, filmto the modern day with digital cameras and camera phones. Camera obscura (Before 17th century) The forerunner to the photographic camera was the camera obscura. Camera obscura (Latin for "dark room") is the natural optical phenomenon that occurs when an image of a scene at the other side of a screen (or for instance a wall) is projected through a small hole in that screen and forms an inverted image (left to right and upside down) on a surface opposite to the opening. The oldest known record of this principle is a description by Han Chinese philosopher Mozi ( 470 to 391 BC). Mozi correctly asserted that the camera obscura image is inverted because light travels in straight lines from its source. The use of a lens in the opening of a wall or closed window shutter of a darkened room to project images used as a drawing aid has been traced back to . Since the late 17th-century portable camera obscura devices in tents and boxes were used as a drawing aid. Before the invention of photographic processes, there was no way to preserve the images produced by these cameras apart from manually tracing them. The earliest cameras were room-sized, with space for one or more people inside; these gradually evolved into more and more compact models. By Niépce's time, portable box camera obscurae suitable for photography were readily available. The first camera that was small and portable enough to be practical for photography was envisioned by Johann Zahn in 1685, though it would be almost 150 years before such an application was possible. Ibn al-Haytham ( 965–1040 AD), an Arab physicist also known as Alhazen, wrote essays about the camera obscura, including experiments with light through a small opening in a darkened room. The invention of the camera has been traced back to the work of Ibn al-Haytham, who is credited with the invention of the pinhole camera. While the effects of a single light passing through a pinhole had been described earlier, Ibn al-Haytham gave the first correct analysis of the camera obscura, including the first geometrical and quantitative descriptions of the phenomenon, and was the first to use a screen in a dark room so that an image from