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The EPZ Beginner's Guide to photography - Welcome to the first part of the ePHOTOzine Beginner's Guide to Photography. In this section we are going to be looking at how the digital camera works and how images are processed and saved inside the camera.
First of all, it is important to understand the differences between the two types of camera. There are compacts, which as the name suggests, are smaller, and are used for snapshot type photography, and the SLR (Single Lens Reflex) which are designed for the enthusiast and more professional photographer, and allow more creative control, as well as producing higher quality images. There are also some physical differences between the two types of camera. For example, many compacts do not have an optical viewfinder for you to look through at the subject. Instead the images are framed via the colour screen on the back of the camera. This is the LCD screen.
SLRs do have an optical viewfinder which shows exactly what the camera itself sees and will take as the picture. This works as follows. Light from the subject passes through the camera lens – the glass on the front of the camera, into the camera body and is reflected by a mirror up to a prism and then out of the optical viewfinder, which is what you look at. When the picture is taken, the mirror moves out of the way and the light passes directly to the recording device, which in digital SLRs, is an electronic chip.
Example of an SLR camera.
The lens is the eye of the camera, the aperture is the hole inside the lens which determines the amount of light passing through the lens. The shutter is a curtain inside the camera that keeps light off the recording element until a picture is being taken, then closes again. There are several different ways the amount of light can be controlled by adjusting certain settings on your camera, such as changing the size of the aperture or hole, or altering the length of time that the shutter moves out of the way for. This is called the shutter speed. These functions will be discussed in more depth in the following weeks. What is important here is that you understand first how your camera actually works.
Example of a digital compact camera.
On an SLR the lens is composed of a focus ring, a zoom ring (if it's a zoom lens) and also houses a small switch to select between manual or automatic focus. It is attached by two interlocking plates, and can be correctly lined up by the matching up of two red spots – or on some cameras such as the Canon 400D, two white squares. The lens can then quickly be removed by pressing a small release button down in the bottom right as you face the camera. When set to automatic focus, pressing the fire button on the camera will activate the camera's automatic focussing mechanism. Focussing is the process by which the target point of the image is made sharp and clear. If focussing is set to manual, then you have to adjust the focus ring yourself so that the key part of the image you want to be sharp and clear, is just that.
Lenses come in all different shapes and sizes for a variety of photographical purposes, for example, some are designed specifically for close ups – these are called macro lenses, while others are designed to take in wide viewpoints – these are called wide angle lenses, while others bring you closer to the action and these are called telephoto lenses. On a compact camera, the lens is not interchangeable, so it is a zoom lens, capable of going from wide angle, to telephoto. This is called an optical zoom. Digital zoom is where the camera itself, crops into the picture using digital processes. This should be avoided as it either degrades the image quality, or lowers the size of the image.
When a picture is taken, the shutter opens rapidly and stay open for the length of the exposure. This is set by the shutter speed. It can be a very short time, a fraction of a second, or a second long, which is known as a long exposure. In this digital age, images are exposed onto an electronic chip called a sensor and the developing process is all done inside the camera very rapidly. These chips are made up of millions of light-sensitive, mini-sensors which convert the light into the tiny dots that make up a digital image. These are called pixels and the more of them that are in an image, the more detailed it becomes. This is why cameras are often marketed on the size of images that they produce, which is measured in megapixels, a term which represents amillion of these pixels .
Once an image has been created and developed inside the darkroom of your camera, it is then saved to either internal memory, or a removable memory card. There are various types of memory cards which are all an arrangement of silicon chips on which the camera records information. They are different from computer memory, in that information, or pictures, are not lost when the camera is turned off. In this way, memory cards are more like computer hard drives in terms of keeping information. In fact, one type of memory card, the MicroDrive, is just that, a miniature hard drive. Memory cards are measured in terms of gigabytes or megabytes, depending on how much information the card can store. The higher the memory of the card, the more expensive they are likely to be. From here the images can be uploaded straight onto a computer via a device such as a USB lead or memory card reader.
In next week's guide we will be looking at Image Resolution in more detail and how to use different size images for different pursposes.
All photographic images in this review were taken with the Canon EOS 400D.