Basics of a Camera


The traditional camera (the still film camera) is basically made of three major components: a lens (optical component), the film (a chemical element) and camera body (the mechanical part).

The lightproof box that is the camera, allows, at the right moment, some bit of light to enter the camera through the lens. Light changes speed and direction as it moves through different medium, say, from air to glass, slowing down in the glass (lens). The movement of light through a convex glass produces the same image as the one in front of the camera (figure 1 below).

candleFigure 1: Candle through a hole similar to the aperture

The path of the light in the glass depends on the angle of entry (determine by distance of the object in focus) and the structure of the lens (total angle to bend the light beams). What we normally refer to as ‘focusing’ just involves aligning the object so that it falls directly on the surface of the film. The lens (a combination several lenses into one unit) will ultimately determine the nature of bends and the path of the light beams.

When you want to take a photo of an object, you will focus the camera towards the direction of the object. Light reflects off the object and bounces into the camera through the lens and then onto a mirror. Single-lens-reflex (SLR) cameras have a special prism called pentaprism, which ensures that a beam of light is constantly deviated at 90° (ordinarily the deviation of light is dependent on the angle of entry). The light then bounces off the mirror into the pentaprism, then into the eyepiece before finally landing into your eye. This allows you to see the image exactly as it will appear on film. This journey of the light enables you to see the object exactly the same way its seen at the film.

The clicking of the camera button is actually the recording of reflected light off the objects in the camera’s field of view. When you click the button, it operates a mechanism called the shutter, which involves brief opening of the aperture to make a hole in front of the camera, thereby letting in some light to enter through the lens and exposes the film. The film is made of special materials that react to light as it passes through the camera to store the object

Although digital camera resembles the film cameras in all aspects, its operation is very different. Unlike film cameras, they capture and record images using digital technology, storing images as strings of numbers instead of patterns of light. When the light hits the lens after the aperture opens, the incoming light rays is captured by an electronic component (remember it has no film) that converts them into electrical signals. The electronic component actually breaks up the light reflected off the photographed objects into millions of tiny dots and squares called pixels.

Major Parts of a Camera

There are myriad of parameters that go into production of a photograph, which creates a room for countless opinions on the various aspects of this art. For instance, while to some the most important part of a camera is the lens, others rank the image sensor as the number one part of a camera. However, there is consensus that the different parts of a camera compliment each and therefore it would be improper for any to claim credit on its own.

I am therefore going to highlight the major parts that make a camera regardless of the type of the camera.

  1. Lens: Camera lens is certainly a critical component of the camera. The process of making a photo starts with the entry of the light through the lens. This part of the camera is therefore the foundation upon which the end product (photos) will stand. Lenses have different characteristics; focal length, aperture, lens ratio, some are fixed and others interchangeable. There are different types of lenses suited for different aspects of photography.

lensesFigure 1: Image of lenses

  1. Sensor: Being photosensitive (react to light), when the light photons collected from the admitted light through the lenses hit the image sensors, some electrical charge is produced. The work of the image sensor in a camera is therefore to convert the optical image to an electronic signal. The electronic chips that make the sensor could be CMOS type (Complementary Metal Oxide Semiconductor) or CCD (Charge-Coupled Device), with each suited for different method of performance.

sensorFigure 2: A typical sensor arrangement

  1. Aperture: As indicated above, the work of a camera lens is to collect light. The aperture (the diameter of a lens) refers to the opening of a lens’s diaphragm through which light is admitted. The iris (an adjustable opening), controls the amount of light coming through the lens, what we generally refers to as ‘exposure’. This control by the iris determines the light that reaches the image sensor. While digital compacts have fixed aperture lens (fixed diameter), modern cameras offer ranges calibrated in f-stops, which is expressed as numbers e.g. 2.8, 4 and 16.
  2. Viewfinder: A camera viewfinder is what the person taking the photograph looks through to compose or focus. While the viewfinder is found in all DSLR (Digital Single Lens Reflex) cameras, they are not available in all the models of the digital compact cameras that have replaced it with an LCD (Liquid Crystal Display) screen.
  3. Shutter: A camera shutter is a like curtain in front of the camera sensor that stays closed until the camera fires. When the camera fires, the shutter open and fully expose the camera sensor to the light that passes through the lens aperture. The length of time the shutter is left open/ exposed is determined by the shutter speed.
  4. Memory Card: This is the store of the images in the camera and varies in capacity, speed and backup measures. While some cameras come with inbuilt memory, a variety of plugin memory cards are available to increase the storage capacity. You will need a memory-card reader or a USB cable to transfer the photos from the camera to your computer or other devices. Different types of memory cards include SD (Secure Digital), SDHC (Secure Digital High Capacity), SDXC (Secure Digital ‘Xtra Capacity’), CompactFlash (CF), xD (eXtreme Digital), Multi Media Cards (MMC) among others

sdFigure 3: A camera memory card

  1. LCD Screen: The LCD screen is used to preview and view the photos after the shooting and is therefore replacing the viewfinder.
  2. Flash: The role of the flash in photography is to provide extra light in situations of low light and dim light. Nearly all cameras (save for some professional category DSLRs) have on-board flashes.

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