Pinhole Camera: Principle, Construction, Properties

Pinhole Camera: In the present day and time, we all use cameras. Some of us use it daily, and others use it every hour. Cameras are in our phones, tabs, laptops, satellites sent to outer space, etc. The human eye behaves like a camera too. But what is expected in all these cameras are lenses. Some cameras have more than one lens, and some have bigger or high-powered lenses, but all the cameras we have around work with lenses. But there is an exception, and it is called a Pinhole Camera.

A lens in a camera helps in image formation, but is it possible to create a camera without a lens? Yes, a Pinhole CAMERA! Anyone can easily make a pinhole camera right in their homes using the most basic material available. Continue reading this article to find out what a pinhole camera is and the science behind how they work.

Working of Pinhole Camera: What is a Pinhole Camera?

It is the most basic and simple kind of camera. A pinhole camera needs no lens. As its name suggests, this camera has a “pinhole” sized opening that allows the light rays to focus within a limited space and form a clear image. The image created by a pinhole camera is real and inverted.

A pinhole camera is based on the theory of Camera Obscura. The Latin word “Camera Obscura” means “darkened room”. It describes a device in a shape of a box or a room that lets the light through a small opening on one side and projects it on the other. In this way, the image of an object is outside the box. The latest and most complex cameras use mirrors and lenses to project images upwards or right-side-up, which are used for much more advanced photography. In contrast, Camera Obscura is used for drawing and entertainment.

The Greek philosopher Aristotle noticed in the \(4^\rm{th}\) century that light from a solar eclipse that passes through holes between the leaves, projects an image of an eclipsed sun on the ground. In the 4th century B.C, Euclid noticed a straight light passing. Alhazen (also known as Ibn al-Haytham), in the 11th century, while experimenting with camera obscura, suggested that when a screen is used, an image from one side of a hole in the surface could be projected on the other screen. The development of a pinhole camera employed the knowledge obtained by the research done by all these scientists and mathematicians. In 1850, Sir David Brewster captured the first known image using a pinhole camera.

What is the Working Principle of Pinhole Camera?

Let us try to understand the working principle of a pinhole camera using a simple diagrammatic representation given below.

Pinhole cameras are based on the principle of rectilinear light motion, according to which light travels in straight lines. Due to the straight-line motion of the light, an inverted image is formed by a pinhole camera. With the appropriate dimensions of a pinhole camera and the size of a tiny hole from which the light enters, we can take an image of the same quality as possible using a digital SLR camera. Pinhole cameras are characterised by the fact that they do not have a lens. A camera with a lens can never be a pinhole camera.

Construction of a Pinhole Camera

A pinhole camera can be uniquely designed by the photographer based on how he wishes to use it. A basic design of a photographic pinhole camera includes a light-tight box with a pin-sized hole opening at one end, and on the other end, it has a piece of film, or photographic paper wedged or taped. A shutter can be fashioned using a cardboard flap with a tape hinge. The pinhole may be punched or drilled using a sewing needle through a tin foil or thin aluminium or brass sheet.

This piece is then taped to the inside of the light-tight box behind a hole cut through the box. A cylindrical cornflakes container or a shoebox may be made into a pinhole camera. One thing that inspires many pinhole photographers is the art of building their cameras; finding new materials or a perfect box is equivalent to finding a hidden treasure.

Working of a Pinhole Camera

Imagine yourself inside a dark room that allows no light inside to understand how a pinhole camera Imagine yourself inside a dark room that allows no light to understand how a pinhole camera works. Now imagine that a small opening is made on a wall right in front of you. When a person outside your room holds a torchlight, the light from the torch would be seen by you as it seeps through that hole. The amount and direction of light entering through that hole vary as the person holding the torch on the other side of the door moves about the room.

Now in place of a room, consider a small light-proofed box with a small pin-sized opening on one side of the box. At your place, now, there is a film inside the box which captures light rays. The film inside the box records the image rather than looking at the image of light rays hitting the opposite side of the wall. The box’s exposure to the light has to happen over a prolonged period because the size of the pinhole opening limits the light entering the box.

We do not have to focus on a pinhole camera like ordinary cameras; they are always focused. But on bringing a pinhole camera very close to the object, the size of the pinhole effectively increases, and the image appears blurred. The inside of the pinhole camera is blackened to avoid any unwanted reflections inside, and it also helps to have a light shield over the back to shade the screen. The clear image formed using a pinhole camera is excellent evidence that light travels in straight lines.

A much sharper image can be formed using a small pinhole than a larger one. However, if the size of the pinhole is reduced to a point size or so, light waves may be scattered slightly at the edges of the pinhole and cause distortion or loss of focus. Smaller holes also increase exposure times since they will let less light into the camera.

Properties of the Image Formed by a Pinhole Camera

Check the properties of the image formed by a pinhole camera and other details of pinhole camera images below.

1. The pinhole camera forms a real image, and we can obtain this image on a screen.
2.  The image formed is smaller in size compared to the object.
3. The image formed is inverted on both the \(x\) and the \(y\)-axis.
4. The image can be used to analyze the rectilinear propagation of light.
   
5. The size of the image formed by a pinhole camera depends on the screen’s distance or film behind the pinhole.
6. Multiple images will be obtained on the screen on making multiple pinholes.
7. A bigger pinhole will allow more light to get in; thus, light from one point on the object can reach more than one point on the screen. Hence, the image will be brighter but blurred.

How Do You Make a Simple Pin Hole Camera?

As mentioned at the beginning, one can make a Pinhole camera at home using just a handful of easily available materials. You can create one, too, right after reading this article!

Pinhole cameras are inexpensive and are easy to make. Using simple materials available at home, we can all design our own pinhole cameras. The step-by-step construction of a pinhole camera is as given below:
Step-1: Take a small box like a shoebox, coffee can, or cylindrical chip box.
Step-2:  Using black paint, colour the inside of the box entirely to make it light-proof.
Step-3: Using approximations, calculate the appropriate distance between the film and light source and then make a small circular hole at the bottom of the box using a needle or a toothpick.
Step-4: Use a thick piece of black chart paper and cut it into 2×22×2 inches to make a shutter for the camera.
Step-5: Use sturdy duct tape and use it to tape the shutter in front of the pinhole.
Step-6: A light adhesive can control the light entering the box from the shutter flap.
Step-7: Make a viewfinder out of cardboard.
Step-8: Place a bright stationary object in front of a pinhole camera to get an inverted impression that can be seen on the screen.

Step-9: Cover the pinhole camera with a thick black cloth instead of a shutter, and replace the screen with a photographic film to get an actual photograph.
Step-10: Put the camera towards the objects to be photographed, and remove the black cloth only from the side of the pinhole, exposing it to the light coming from the object through the pinhole.
Step-11: Get the picture developed and printed in the studio.

Applications and Use of a Pinhole Camera

Here are some of the most common applications of a pinhole camera.

1. To safely observe a solar eclipse, the image formed by a pinhole camera can be produced on a translucent screen in real-time. You can understand this better with the help of the image given above.
2. A common use of pinhole photography is to capture the sun’s movement over a long period.
3. Pin-hole cameras are made from materials that electric or magnetic fields can not detect. That is why these are often used for surveillance because they are difficult to spot.
4. Their manufacturing costs are lower, and they are lightweight, making them a convenient option for scientific photography at schools.
5. Making a hole in each side of the camera box and using a cylindrical roll to mount the film in the centre makes it possible to obtain 360° photos using a pinhole camera.

Summary

A pinhole camera needs no lens. As its name suggests, this camera has a “pinhole” sized opening that allows the light rays to focus within a limited space and allows the formation of a clear image. The image formed by a pinhole camera is real, inverted, and smaller than the object. The simplicity of a pinhole camera is amazing. It consists of a light-proof container with light-sensitive material at one end and a pinhole at the other shielded by a small shutter in its most basic form.

When the shutter is opened, light enters the box through the hole to imprint an image on photographic paper or film placed at the camera’s back. We use pinhole cameras to safely observe a solar eclipse and capture the sun’s movement over a long period.

FAQs

Let us look at frequently asked questions in the below-mentioned section.

Q.1. What is a pinhole camera?
Ans: A pinhole camera is a camera that works without a lens to produce a real, upside-down, and diminished image of an object.

Q.2. What is the working principle of a pinhole camera?
Ans: The pinhole camera works on the principle of the rectilinear motion of light, which states that light travels in a straight line.

Q.3. Write the characteristics of the image formed by a pinhole camera.
Ans: The image formed by a pinhole camera is real, inverted, and diminished in size compared to the original object.

Q.4. What happens to the image if the size of the pinhole is increased?
Ans: When the size of the hole in a pinhole camera increases, the amount of light entering the box increases, then the sharpness of the image obtained decreases, and the image appears thick and blurry.

Q.5. Write the advantages of using a pinhole camera?
Ans: The advantages of a pinhole camera are as follows:

1. It is inexpensive
2. It is easy to use
3. It is easy to construct
4. It offers great depth in images

The article gives detailed information on the Pinhole Camera and its properties. We hope you find this article helpful and is able to be of use in your exam preparation. If you have anymore doubts, please reach out to us and let us know in the comments section below. We will get back to you at the earliest.

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