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W H A T I S A P I N H O L E C A M E R A ?

A pinhole camera, also known as camera obscura, or "dark chamber", is a simple optical imagingdevice in the shape of a closed box or chamber. In one of its sides is a small hole which, via

the rectilinear propagation of light, creates an image of the outside space on the opposite side ofthe box.

History*

Images created via a small opening will be found in the natural environment and in everyday life,

and people in various parts of the world have been observing them since ancient times. Probablythe earliest surviving description of this kind of observation dates from the 5th century BC, writte

by Chinese philosopher Mo Ti. In the Western hemisphere, Aristotle in 4 BC was asking, withoutreceiving any satisfactory answer, why sunlight passing through quadrilaterals, for example, one

of the holes in wickerwork, does not create an angled image, but a round one instead, and whythe image of the solar eclipse passing through a sieve, the leaves of a tree or the gaps between

crossed fingers creates a crescent on the ground. In 10 AD the Arabian physicist andmathematician Ibn al-Haitham, known as Alhazen, studied the reverse image formed by a tiny ho

and indicated the rectilinear propagation of light. There was another scholar during the MiddleAges who was familiar with the principle of the camera obscura, namely the English monk,

philosopher and scientist Roger Bacon. It was not until the manuscriptCodex atlanticus

(c. 1485that the first detailed description of the pinhole camera was set down by Italian artist and invent

Leonardo da Vinci, who used it to study perspective.

Initially, the camera obscura was, in fact, a room where the image was projected onto one of the walls through an opening in the opposite wall. It was used to observe the solar eclipse and to

examine the laws of projection. It later became a portable instrument which was perfected witha converging lens. Instruments of this kind were often used as drawing aids and, at the dawn of 

photographic history, they formed the basis for the construction of the camera. The pinhole camewas finally also applied in modern science – during the mid-20th century scientists discovered th

it could be used to photograph X-ray radiation and gamma rays, which the ordinary lens absorbs.As a result, the pinhole camera then found its way onto spacecraft and into space itself.

While the first photograph taken with a pinhole camera was the work of Scottish scientist Sir Dav

Brewster back in 1850, the technique became more established in photography during the late19th century when it was noted for the soft outlines it produced, as opposed to lenses generating

perfect, sharp images. The pinhole camera was later abandoned and it wasn't until the end of the 1960s that several artists began using it in their experiments, thus awakening renewed

interest in this simple photographic apparatus which endures to this day.

Diagram of a pinhole

camera.

 Principle and characteristics

As mentioned above, the image in the pinhole camera is created onthe basis of the rectilinear propagation of light. Each point on

the surface of an illuminated object reflects rays of light in alldirections. The hole lets through a certain number of these rays which

continue on their course until they meet the projection plane wherethey produce a reverse image of the object. Thus the point is not

reproduced as a point, but as a small disc, resulting in an image whichis slightly out of focus. This description would suggest that the smaller

the hole, the sharper the image. However, light is essentially a wavephenomenon and so, as soon as the dimensions of the opening are

commensurable with the dimensions of the light wavelength, diffractionoccurs. In other words, if the hole is too small, the image will also be

out of focus. The calculations for the optimal diameter of the hole inorder to achieve the sharpest possible image were first proposed by

Josef Petzval and later perfected by British Nobel prizewinner Lord

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Why pinhole cameraimages are out of focus.

Rayleigh (see Making the pinhole). He published the formula in his bookNature in 1891, and it is still valid today.

The image created by a pinhole camera has certain characteristicswhich we won't find in classical lens photography. Since the process

entails a central projection, the images in the pinhole camera are

rendered in ideal perspective.Another special characteristic is the infinite depth of field which, ina single photograph, allows objects to be captured with equal

sharpness whether they are very close up or far away.

The pinhole camera takes in an extremely wide angle. The rays of light,

however, take much longer to reach the edges of the negative thanthe centre, thus the picture is less exposed along the edges and

therefore darkens.

A certain disadvantage of the pinhole camera is the amount of light

allowed through (small aperture), which complicates and sometimesprevents entirely the photographing of moving subjects. Exposure time

is normally counted in seconds or minutes but, in bad lighting

conditions, this could be hours or even days (see Determining exposuretimes for pinhole cameras).

 

You can transform any light-proof box into

a pinhole camera.

Sample photograph: 1

 

Pinhole Cameras

Constructing a simple pinhole camera is easy. Make a hole in one side

a closable box made of material which doesn't let light in. Place a thinpiece of metal or tin can with a tiny hole over the opening. On

the outside of the box stick a strip of black tape over the opening whicacts as the release. Then, in a dark room, attach a piece of film or

photographic paper onto the opposite side and the camera is ready.

The pinhole camera's simple construction offers a number of ways inwhich it can be constructed, using various materials. The cameras can

all kinds of shapes and sizes, with various formats and types of light-sensitive material, several holes, curved film planes, for panoramic

images etc. There are all sorts of imaginative ways to make thesecameras; the most ordinary of objects can unexpectedly become pinho

cameras, for example a matchbox, book, a pepper, travel bag, a delivevan, an old fridge or even a hotel room. You can, of course, turn your

ordinary camera into a pinhole camera by simply replacing the lens wi

a small hole. And to complete the list, there are also a number of commercially produced pinhole cameras in existence, on the whole,

highly elaborate models.

What you experience once you design, construct and try out your own

pinhole camera is difficult to describe. You'll find yourself on a wholenew plane of imagination, experimentation and creativity. Moreover,

the photos themselves have an unusual atmosphere and capturethe world in a different way than you are used to

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Diagram from 1685 showing how rays of light travel through the camera obscura, and how the size of the image depends on its distance from the hole,

according to Johann Zahn.

P i n h o l e c a m e r a

From Wikipedia, the free encyclopedia

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Principle of a pinhole camera. Light rays from an object pass through a small hole to form an image.

A home-made pinhole camera (on the left), wrapped in black plastic to prevent light leaks, and related developing

supplies.

A pinhole camera is a simple camera without a lens and with a single small aperture 

— effectively a light-proof box with a small hole in one side. Light from a scenepasses through this single point and projects an inverted image on the oppositeside of the box. The human eye in bright light acts similarly, as do cameras usingsmall apertures.

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Up to a certain point, the smaller the hole, the sharper the image, but the dimmerthe projected image. Optimally, the size of the aperture should be 1/100 or less of 

the distance between it and the projected image.

A pinhole camera's shutter is usually manually operated because of the lengthyexposure times, and consists of a flap of some light-proof material to cover and

uncover the pinhole. Typical exposures range from 5 seconds to hours andsometimes days.

A common use of the pinhole camera is to capture the movement of the sun over a

long period of time. This type of photography is called Solargraphy.

The image may be projected onto a translucent screen for real-time viewing(popular for observing solar eclipses; see also camera obscura), or can expose

photographic film or a charge coupled device (CCD). Pinhole cameras with CCDs areoften used for surveillance because they are difficult to detect.

W h a t i s r e c t i l i n e a r p r o p a g a t i o n o f l i g h t ?

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What is rectilinear propagation of light?

 The formation of shadows with sharp edges demonstrates the rectilinear propagation of light, i.e. the fact

that light travels in straight line.

Rectilinear Propagation of Light is the tendency of light to only travel in straight Lines.

This means that if light "criss-crosses" between each other whilst going through a small hole, you will see

the image upside down, as the light goes straight up from down, and down from up.

In a homogenous transparent medium light travels in a straight line and this is known as rectilinear 

 propagation of light. This can be demonstrated by the following experiment:

Take three cardboards A, B and C and make a pinhole at their centres. Place a burning candle on one side of 

the cardboard A and arrange the cardboards in such a way that the three pinholes and the candle flame are ina straight line. The candle flame will be visible through the pinhole of the cardboard C.

 Now slightly displace any one of the cardboards and try to see the flame through the pinhole of thecardboard C. The flame will not be visible. From this it is clear that light travels in a straight line.