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nelson mandela bay's family lifestyle
author:
xandre van der berg
so this is how a camera works
issue:
8, summer 2008
Photography is undoubtedly one of the most important inventions in history - it has truly transformed the way people percieve our world, and in many ways, has transformed people’s view of art and its place in society. Now we can "see" all sorts of things that are actually many miles - and years - away from us. Photography allows us to capture moments in time and preserve them for years to come. Let's find out how this works. “Camera” means “chamber”, and in fact the first cameras really were chambers. Artists used the camera obscura, or pinhole camera, to project an upside-down image of a brightly-lit scene onto a canvas. The artist could then trace the outlines of the scene and make a drawing of it. The first efforts to permanently record images made by light were done by inventors such as Joseph Niépce, Jacques Daguerre, and William Fox Talbot. Every camera is essentially a lightproof box, with some method of letting in just a small amount of light, at just the right time, for just the right duration. Once the light is in the box, it forms an image, causes a chemical reaction on photographic film, or energizes a photocell. To find out how the light gets in to do its thing, let's imagine what happens when you snap a picture, maybe of a dolphin playing in the surf. One kind of camera — which can be either a digital camera or a traditional film camera — is called a single-lens reflex (SLR) camera. In this camera, there is only a single set of lenses for both viewing and photographing an image. Let's say you spot your dolphin and lift your camera to your eye. What happens? First, light bouncing off the dolphin passes into the camera, through a set of lenses, and onto a mirror. From there, the light bounces up and into a funny-shaped piece of glass called a pentaprism (penta means five, and the pentaprism has, you guessed it, five sides). Once light enters the pentaprism, it bounces around in a complicated way until it passes through the eyepiece and enters your eye. The dolphin is swimming just below the water, but you have a feeling it's about to surface. Wait for it, wait for it … there! You snap the picture. When you press the button on the camera, the mirror flips up out of the way. Instead of bouncing into the pentaprism, light from the dolphin passes directly to the back of the camera. There, it either hits photographic film and starts a chemical reaction, or else it impacts an array of light-sensitive cells that releases a tiny electric charge in each activated cell. Either way, even though the dolphin's long gone, you've captured its image. Congratulations, you've taken a photograph! SLR's are not the only camera type. Many of us use direct vision compact cameras or just “compacts”. In this camera, the lens for viewing is separate from the lens we use to take photographs. Because of the two sets of lenses, compacts don't need a pentaprism or a hinged mirror, making them smaller and lighter than the SLR's. Once the light has exited the lens, it is projected onto the film surface. This is made up of minute light-sensitive elements, each of which undergoes a chemical reaction when it is exposed to light. When the roll is developed it is exposed again, but this time to a series of chemicals. The reaction that occurs this time depends on the type of film; in black and white film the developing chemicals make the exposed light-sensitive elements darker, and vice versa. Colour film, on the other hand, is made up of particles which react differently to red, green and blue light, each of which are on an individual layer of film. The flash on a camera is our attempt to light up a scene that is too dim, in order to show up well, either on film or electronically. The Operation of a Digital Camera The digital camera is truly different from its predecessor the film camera. Digital cameras have a built-in computer, and all of them record images electronically. The operational basics of a digital camera are similar to the workings of a manually operated camera. The difference being the method used to store the image and the number of images that can be stored in the device. Just like a conventional camera, a digital camera has a series of lenses that focus light to create an image of a scene, but instead of focusing this light onto a piece of film, it focuses it onto a digital sensor. These sensors are nothing but computer chips. The computer chip breaks the electronic information down into digital data, a language that computers recognize - bits and bytes. Essentially, a digital image is just a long string of 1s and 0s that represent all the tiny colored dots - or pixels - that collectively make up the image. The term megapixels, is a measure of the number of sensor elements of the camera - the higher the number of megapixels, the better the resolution of the electronic picture. The digital camera makes use of a memory card. The number of images that can be stored on this card varies according to its memory capacity. You can also delete the electronically stored images if you do not like them. With digital photography, not only can pictures be taken at will, but they can be downloaded to a computer and sent all over the world with just a few clicks of the mouse.
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