Did you know? The human eye has the equivalent of 120 million pixels - 5 times more than a typical camera!
A camera is tool made up of many components that work together in order to see a three-dimensional, real-life scene and record it to the camera as a two-dimensional image. The parts are similar in function to those used by the human eye and mind to accomplish the same task. Below I cover the basic components of the camera so that you are familiar with your tool and can use it to create a photograph.
Light from a scene first travels through the lens. This component is comprised of glass elements housed in a cylindrical barrel made from plastic and/or metal. Its job is to gather a large amount of light from the scene and also to focus the light from a plane of the scene to create a visibly sharp image. For more on lenses, read "Lesson 2: Knowing Your Lens".
Within the lens there is the diaphragm, which is a group of blades that move to regulate the size of the opening at the centre of the lens. This opening is called the aperture. Changing the size of the aperture affects two characteristics of an image: a) the brightness, and b) how much of the image appears in focus. The larger the aperture, the brighter the image and the less that appears in focus. The smaller the aperture, the dimmer the image and the more that appears in focus.
Once light exits through the lens, it travels through the viewfinder assembly. Comprised of a mirror and a glass prism, the viewfinder reflects the incoming image up and out the back of the camera. This real-time image can be seen by the photographer and used to aim at the desired scene.
When one decides they want to record the scene, they press a button on the camera to activate the shutter. This is a flat, rectangular component consisting of two metal curtains. In their normal state, the curtains stop the light from advancing further into the camera. When the shutter button is pressed, the first curtain moves across the shutter plane to create an opening and allow light to pass through. The second curtain then follows behind to close this opening. How soon the second curtain follows the first is called the shutter speed. The shutter speed affects two characteristics of an image: a) the brightness, and b) the amount of motion blur of a moving object. The faster the shutter speed, the dimmer the image and the less motion blur. The shower the shutter speed, the brighter the image and the more motion blur.
The light that passes through the shutter next hits the sensor of the camera. Also rectangular in shape, the sensor is comprised of an array of millions of microscopic sensor elements, called pixels, that are sensitive to light. Some pixels record the color blue, some record the color red and some record the color green. Each pixel registers the cumulative light that it senses by converting it to an electric signal and recording the strength of that signal as a number. The result is an array of value pairs containing the colour that was recorded and its brightness level. These values represent the image of the real life scene captured. The resultant image is stored on a memory card inside the camera.
On the back of the camera is found an LCD screen that has for functions:
Monitoring the camera settings
Playback of the recorded images
Accessing the camera menus
Viewing a real-time image of the scene
The last function is called Live View and is toggled on and off by pressing a button on the camera. This moves the mirror up so that it no longer reflects the image through the viewfinder and allows it to travel straight through to the sensor. Here the image is read continuously and displayed on the LCD screen. During Live View, one can magnify the view of a portion of the scene in order to verify that it appears in focus.