When shopping for professional digital SLR cameras, you may see some that advertise the “Four-Thirds 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.  Seven cameras manufactures—Fuji, Kodak, Leica, Olympus, Panasonic, Sanyo, and Sigma—have agreed upon a standard design allowing 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 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 color 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 center of the image rather than the whole image.  This results in the center 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 system is still fairly new—five years old at the most—and only adhered to by seven 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 system camera 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.

What exactly is “face detection technology”, and why is it considered a valuable asset in a digital compact camera?  Part of the confusion about this feature is caused by its rather vague name—“face detection”—that sounds more like something out of a James Bond movie than a photography store.  This article will explain what face detection is, how it works, and why it’s useful in a camera.

First, let me describe the problem that face detection technology in a digital compact camera solves.  Have you ever taken a picture of a person in which the flash from the camera washed out their face, to the point where you can only make out a pale blob with a pair of eyes and lips in it?  This phenomenon usually occurs where taking a picture indoors or outdoors in dim lighting.  When the picture is taken, the flash is too bright.  The light reflects off the person’s skin (usually the face) back at the camera, through the lens, and onto the film or image sensor where, because the flash was too bright, the image of the person’s face ends up being overexposed and consequently washed out.  It is possible to avoid this, however, by manually adjusting the exposure and flash levels.  This takes time, however, and thus is only really practical for posed pictures—and a lot of amateur photographers like snapping quick, candid photos that capture a second of true life.

What face detection does is identify the face of the person in a framed shot, calculate the proper exposure levels to get the best image of the subject’s face in the picture, and then adjusts the flash level accordingly.  It does all this in less than a second, of course.  The result is a photograph where the person’s face is clearly visible in all its lifelike color and detail.

How does a digital compact camera even know part of the framed image is a face in the first place?  The answer is to that is complicated, involving technical computer jargon and mathematical algorithms.  Put simply, a computer program in the digital camera defines a face as a pre-defined set of shapes and colors.  When you frame a shot through the viewfinder, the computer program scans the image looking for the “face pattern” of shapes and colors until it identifies one.  Of course, when you turn your head, the shape changes.  Consequently, digital cameras are best able to identify faces when the subject it looking straight at the camera, and has more trouble with faces in profile or looking up, down, or to the sides. 

Considering how impressive and useful this technology is, one would expect to find it as an advanced, high-end feature in expensive, professional cameras with price tags running into the thousands of dollars.  Surprisingly, this is not the case.  Face detection technology is becoming increasingly common in inexpensive digital compact cameras aimed at the family market.  The average compact camera targeting the amateur family photographer usually runs between $100 and $350 dollars. 

Face detection technology starts becoming commonly available in the midrange cameras around the $200 level, such as the Sony Cybershot series or the Casio Exilim series.  Of course, face detection is becoming a standard element in the more expensive higher-end compact cameras, such as the Canon PowerShot G10 retailing for around $500.  Even some of the inexpensive low-end digital compact cameras come with face-detection technology, such as the Samsung S860, which sells for under $90.