What is a Pinhole Camera?
The pinhole camera is the simplest kind of camera. It does not have a lens. It just makes use of a tiny opening (a pinhole-sized opening) to focus all light rays within the smallest possible area to obtain an image, as clearly as possible. The simple image formed using a pinhole camera is always inverted.
Images formed by a Pinhole Camera
To understand how a pinhole camera works, imagine yourself inside a dark room which allows no light inside. Now imagine a small opening made on the wall that you are facing. If someone were to hold a torchlight from the outside, you could see that light seep into your room. If the person with the torch moved around the light source, you would see the light seeping in, vary in terms of direction and even intensity.
Now instead of a room, imagine a small box with has been light proofed except for a small pin-sized opening on the box. Instead of you inside, there is a film which captures light rays. Instead of you looking at the image of light rays hitting the opposite side of the wall, the film inside the box records the image. The exposure to the light has to occur for a prolonged period because the pinhole opening limits the amount of light entering.
In a normal camera, a convex lens is used to admit more light while simultaneously focusing all that light to a small area. This reduces the amount of exposure time required. The effect of the size of the pinhole opening on the image formed is illustrated below.
How To Make a Pinhole Camera
You can make a simple pinhole camera with simple materials probably available at your own home. The step-wise procedure has been described below.
- Take a small box like a shoe-box or a coffee can
- Paint the box entirely in black to light-proof it
- Appropriately determine the distance between the film and light source and make your circular pinhole on the bottom of the box
- Make a shutter by cutting a piece of thick black chart paper (2 x 2 inches ideal)
- Use sturdy duct tape to hold the shutter in place
- Use a light adhesive to control shutter flap and light entering the box
- Make a viewfinder out of cardboard
Pinhole Camera Image Characteristics
- A real image is obtained as the image is obtained on the screen.
- The size of the image obtained is comparatively smaller than the actual object.
- The image is inverted on the x-axis as well as on the y-axis.
- The image can be used in the analysis of the rectilinear propagation of the light.
What are the Uses of a Pinhole Camera?
- The image formed by a pinhole camera may be projected onto a translucent screen for a real-time viewing or safe observation of the solar eclipse.
- A common use of pinhole photography is to capture the movement of the sun over a long period of time.
- Pinhole cameras are sometimes used for surveillance because they are difficult to detect.
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