The development of the digital camera occurred primarily in the latter decades of the 20th century. The advent of the microchip, advanced electronics, embedded software and the charge coupled device, all helped to bring about this significant development in photography.
Digital cameras were initially very expensive, but have, over the year, dropped substantially in price, as well as increasing in resolution and features. Many mobile phones now have a digital camera built-in.
Digital cameras opened up lots of new possibilities of what could be done with photographic images. These would not have been possible with the older film cameras. Such possibilities included instant viewing of images on screens, digital manipulation using software, rapid transmission of images over the Internet, and ease of sharing the digital images with family and friends.
In addition to still-photography, modern digital cameras also support the capture of moving images, and sounds. These enable several seconds or minutes of motion pictures to be captured and replayed without having to use a digital camcorder.
Cameras Prior to Digital Cameras
Older, non-digital cameras used film, which was essentially a plastic strip on a roll, and this plastic strip contained light sensitive chemicals, which darkened when exposed to light. A lens focused the light onto the film, and a shutter opened for a split second to allow the light in. This film then had to be processed. This consisted of extracting the film from the protective canister, in a dark-room environment, and placing it in a series of chemical baths which developed the image (converting the light-exposed silver salts to silver), and 'fixed' or stabilised the image, washing away the unexposed light-sensitive chemicals in the film. The film was then washed and dried. The result was a film strip containing dark areas where the film was exposed to the light, and light areas where where unexposed. Thus it was called a "negative".
To produce viewable photographs, a further process of printing was used. This shone light through the negative onto photographic paper. This paper also had light-sensitive chemicals on its surface, and so needed to be handled in a dark-room environment. It would be exposed to the light via the negative for a short time, and then it also had to go through a number of chemical baths to develop, and fix the image. So, the result of two negatives, produced a "positive", and therefore the resulting image would resemble the original scene which was photographed.
Digital Camera Technology
Digital Cameras operate entirely differently. Instead of light-sensitive chemicals on a film, the light is instead focused onto an electronic component called a "Charge Coupled Device" (CCD). This device has thousands of light-sensitve cells. When exposed to photons of light, the cells will build up an electric charge. The more photons striking the cell, the more charge builds up. The greater the number of cells which the CCD has, the greater resolution the final picture will have. Hence manufacturers talk about Megapixels, where each pixel represents the smallest dot out of which the picture is constructed.
Digital Camera Selection
If you are thinking about purchasing a digital camera, the choice and price range is vast, and you will really need to decide how you want to use the camera and how much you are prepared to spend in order to narrow down the choice. The following set of criteria may prove helpful. For each criteria, the actual products available form a spectrum. I may mention the extremes, but the reader should be aware that there is usually a middle ground too.:
- Physical size: Digital cameras range from ultra compact, where the user's top priority is a small size, up to larger units with large lenses (better quality optics), and interchangable lenses for different situations.
- Weight: This is a trade-off which you will have to make. The cameras with the higher quality images, flexible optics, most features, longest battery life are usually heavier because of those things.
- Pixel count: The number of photo detectector cells on the detector. This can range from 3 Megapixels to over 12 Megapixels, where a Megapixels is approximately one million pixels. Camera electronics can increase the number of pixels in the image beyond that using various image processing and anti-aliasing techniques. The larger pixel count cameras would be required for images which are intented to be shown on large displays, e.g. advertising sites in public places. The smaller pixel count cameras are perfectly ok for viewing on small screen devices.
- Zoom: This looks at the optical capability of the camera. At the near end of the zoom you have the ability to have a wide-angle view. At the far end you have a telephoto capability, capable of zooming in on distant objects. In addition to the optical zoom, camera electronics can also zoom in digitally on the optical image. So look at the specifications for both optical and digital zoom. Digital zooming can also be performed after a shot has been taken, and uploaded onto a computer, so the quality of the initial optical zoom is the most important.
- Camera shake protection: In low light conditions, when not using a flash, the CCD needs to be exposed to the light for a longer period. If the camera is not mounted on a stable platform, e.g. a tripod, then it is likely that a hand-held camera will move slightly during this time period, and the image may be blurred. Some cameras offer an image stabilisation feature to help reduce the effect of camera shake.
- Manual focus: Most digital cameras focus the optics automatically, however, some photographers also want manual control in addition for special effects, or when the shooting conditions don't allow the auto-focus to perform well enough.
- Shutter speed: The range of shutter speeds that the camera is capable of. If you intend taking pictures of fast moving objects, e.g. sport photography, you will need a camera which is capable of very fast shutter speeds to avoid too much image blur. On the other hand, if you intend taking long exposure shots, e.g. of the night sky, the shutter will need to remain open for several seconds in order for an adequate amount of light to enter the camera.
- Flash: Some digital cameras have a built-in flash, which you can usually have on, off, or automatic (will flash if needed). Some also have an anti-red-eye setting which causes the flash to activate a few times before the image is captured in order to trigger the subject's eye to reduce its pupil in size and thereby lessen the "red-eye" effect. In addition, some cameras have the ability to be connected to an external flash device, thus enabling better, brighter and more controlled lighting of the subject to be performed.
- Aperture setting: Does the camera allow you to manually set the aperture, that is, the width of the opening through which the light will pass? A wider aperture means more light, and therefore you may be able to reduce the shutter speed for a less blurred image of a moving object. Note, however, that a larger aperture has a downside: reduced depth of field. Depth of field is a measure of the range over which objects at varying distances from the camera will be in focus.
- Shutter speed: Does the digital camera allow you to manually set the shutter speed? The simpler cameras do not, however they may offer a dial where you can choose between a sport mode (fast shutter), and a landscape shot (slower).
- Movie clips: Does the digital camera allow you to record short motion picture clips? With sound? Can you hook up an external microphone? An interesting measure is the duration of clip it can record. The longer this duration, the more memory the digital camera must have. More memory implies more cost, larger size etc.
- Timer: This feature enables you to set a timer (e.g. 10 seconds) after which the digitial camera will take the picture. This is typically used in situation where the photographer sets up the shot, and then moves into the camera range to be part of the picture.
- Viewfinder: The viewfinder shows the photographer what the camera will record, and allows him/her to organise the subjects, and distance from the subjects in order that they all fit into the picture. The types of viewfinders can range from pure electronic ones where the image is shown on a small screen, usually a type of liquid crystal display (LCD), to optical ones, where a mirror or prism reflects the light into the viewfinder which the photographer can look through. Some cameras have both.
- Battery life: How long will a fully charged battery last? Check out the battery technology used. Older NiCd (Nickel Cadmium) rechargeable batteries have less power than the NiMH (Nickel Metal Hydride), which in turn are less powerful than newer more powerful Lithium-ion batteries.
For many, making a choice can be difficult. At times they need the miniture, light one that they can easily keep in their pocket. At other times they want the better quality and more flexible, feature-rich ones. What to do? Some people will try to get a digital camera somewhere in the middle of the range that will be adequate for most circumstances. Others will purchase two (or more) cameras and have the best of both extremes.