When shopping for professional digital SLR cameras, you may see some that advertise the Four Thirds camera System as a selling point. But what exactly is that? The key to understanding the four-thirds system is that it is not a feature or a type of technology, but an industry standard. Some cameras manufactures including Fuji, Kodak, Leica, Olympus, Panasonic, Sanyo, and Sigma—have agreed upon a standard design allowing Four thirds camera lenses and bodies to be interchangeable. For example, one could buy a Panasonic camera and an Olympus telescopic lens, and the two would be compatible. The standard has proven so popular that other companies that haven’t been using the four-thirds design have started producing adapters allowing four-thirds lenses to be attached to their cameras.
The name of the Four Thirds camera system comes from the aspect ratio (the proportion of width and height) of the digital image sensor inside the camera. The 4:3 image aspect ratio of the four-thirds system is a departure from the traditional 3:2 aspect ratio of old 35mm film cameras that many modern digital SLR cameras continue to emulate. The 4:3 aspect ratio, also common in the simpler digital compact cameras, is taken from video cameras, and is the aspect ratio of television and computer screens. The smaller image sensor size and aspect ratio also allows the interchangeable lenses to be smaller and lighter, and the digital SLR cameras themselves to be more compact.
There are a few drawbacks to cameras using the four-thirds system. These problems are common among any digital camera using a digital image sensor smaller than the original size and aspect ratio of 35mm film. First, the picture quality is directly related to the image sensor size—the bigger the image sensor, the better picture quality. Consequently, smaller sensors capture images with a lower pixel count, and a narrower colour range, producing grainier photographs. Secondly, the lens projects a 35mm sized light image—but a four-thirds system digital camera’s image sensor is smaller by about 75% smaller. As a result, it captures just the centre of the image rather than the whole image. This results in the centre of the image having a zoomed-in effect, with the four edges surrounding it being cropped off. This is called the “crop factor”. The four-thirds system has a crop factor is about 2, with even more space lost of the left and right sides due to the different aspect ratio.
The four-thirds camera system is still fairly new and only used by a few companies, so there are as yet only a handful of digital cameras using the system. Luckily, however, they cover a wide range quality and features. The four-thirds system of interchangeable lenses is marketed for professional photographers using high-quality digital SLR cameras, so all cameras using the system would be considered expensive by amateur family photographers. There is still, however, a range of prices. Low-end cameras like the Olympus E-420 and the Leica Digilux 3 are less expensive, but have fewer advanced features. Midrange cameras like the Panasonic Lumix DCM-L10 and the Olympus E-330 offer a balance of quality features and price. Finally, high quality cameras like the Olympus E-3 are packed with advanced features, but are also the most expensive. Which four-thirds camera system product is best for you depends on your specific field of photography—architectural, sports, or social, for example—and a careful examination of each camera’s specifications should reveal which one has the features you need at the best price.