Balko Photo

About the Four Thirds System Standard

The Four Thirds System standard defines a new design and development standards for digital SLR camera systems that make full use of digital cameras and offering a 2X crop factor! The Four Thirds-type image sensor makes it possible for manufacturers to design very compact lightweight lenses. The advantages of the system include more compact telephoto lenses (a Four Thirds lens with a 300 mm focal length would cover about the same angle as a 600 mm focal length lens for the 35 mm film standard) and more even delivery of light to different parts of the sensor.

The Four Thirds System standard was first announced in September 2002 by Olympus Corporation and Eastman Kodak Company of the United States, and is currently also supported by Fuji Photo Film Co, Ltd., Sanyo Electric Co., Ltd., Panasonic, and Sigma Corporation. The name of the system comes from the size type of the image sensor which is referred to as a 4/3 type sensor.

The first such products to be introduced to the market were the Olympus E-1 and related E-System lenses, flash units, and other accessories that were launched by Olympus in October 2003. In December 2004, Olympus also introduced the consumer-oriented E-300 digital SLR. Olympus’s “100% designed-for-digital” concept and technological advances such as the world’s first supersonic dust reduction system.

A major reason for choosing 4:3 for the sensor proportions is that it has historically been the standard for television and became a dominant aspect ratio for computer monitors, as found in the VGA, SVGA, XGA, SXGA+, UXGA and QXGA standards.

Advantages

The smaller sensor size makes possible smaller and lighter camera bodies and lenses. Portability!  One can envision very fast lenses and very high quality lenses at lower costs. You can find this now, to some extent, in the Olympus E-400 and E-410/510 bodies and their kit lenses, and in longer telephoto lenses.

The smaller sensor means that the depth of field is greater than for cameras with a larger sensor.  Compared to a 35mm or full frame camera the depth of field is approx. twice as great. Compared to most other DSLR cameras that use APS-C size sensors the depth of field for a Four Thirds camera is approx. 25% greater.

Because the flange focal distance is significantly shorter than most competing mounts (such as Canon FD, Canon EF, Nikon F and Pentax K), lenses for many other SLR types can be fitted to Four Thirds cameras with simple mechanical adapter rings. (Such mechanical adapter rings typically require manual setting of focus and aperture.)

Some traditional print sizes (5×7″, 8×10″, 11×14″) are closer to a 4:3 aspect ratio than they are the 3:2 aspect ratio, meaning the photographer does not need to crop as much or have large matting to meet these sizes. The same applies for pictures to be used on standard PC screens and non-HDTV television screens.

Disadvantages

Smaller sensors generally yield more image noise. This is most noticeable in low light and with high ISO situations.

There are not as many lenses available as for some of the competing DSLR systems. (As mentioned above, lenses for competing systems can usually be mounted, but with the loss of auto-focus and the need for manual setting of aperture.)