Claims could be based on later versions, since Ignazio Danti added a description of camera obscura in his 1573 annotated translation.In the 4th century, Greek scholar Theon of Alexandria observed that "candlelight passing through a pinhole will create an illuminated spot on a screen that is directly in line with the aperture and the center of the candle." In the 9th century, Al-Kindi (Alkindus) demonstrated that "light from the right side of the flame will pass through the aperture and end up on the left side of the screen, while light from the left side of the flame will pass through the aperture and end up on the right side of the screen." Arab physicist Ibn al-Haytham (known in the West by the Latinised Alhazen) (965–1039) explained in his Book of Optics (circa 1027) that rays of light travel in straight lines and are distinguished by the body that reflected the rays and then wrote: "Evidence that light and color do not mingle in air or (other) transparent bodies is (found in) the fact that, when several candles are at various distinct locations in the same area, and when they all face a window that opens into a dark recess, and when there is a white wall or (other white) opaque body in the dark recess facing that window, the (individual) lights of those candles appear individually upon that body or wall according to the number of those candles; and each of those lights (spots of light) appears directly opposite one (particular) candle along a straight line passing through that window.Distortions in the shapes of animals in many paleolithic cave artworks might be inspired by distortions seen when the surface on which an image was projected was not straight or not in the right angle.The location of the bright circle can be measured to tell the time of day and year.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.Before the term "camera obscura" was first used in 1604, many other expressions were used including "cubiculum obscurum", "cubiculum tenebricosum", "conclave obscurum" and "locus obscurus".
A small enough opening in a screen only lets through rays that travel directly from different points in the scene on the other side and together form an image of that scene when they are reflected on a surface into the eye of an observer.
“Why is it that an eclipse of the sun, if one looks at it through a sieve or through leaves, such as a plane-tree or other broadleaved tree, or if one joins the fingers of one hand over the fingers of the other, the rays are crescent-shaped where they reach the earth?
Is it for the same reason as that when light shines through a rectangular peep-hole, it appears circular in the form of a cone? The oldest known correct answer was given more than 1800 years later in Francesco Maurolico's Photosmi de lumine et umbra (1521).
The image can be projected onto paper, and can then be traced to produce a highly accurate representation.
In order to produce a reasonably clear projected image, the aperture has to be about 1/100th the distance to the screen, or less.
Rays from the head would partly be hidden above (strike above the pinhole) and partly form the lower part of the image.