A teleconverter increases the focal length of the lens currently in use by either 1.4x or 2.0x - depending on the particular model. You do lose a stop or 2 of light when using a teleconverter. A teleconverter is ideal for sports and nature photography, you can turn your Zuiko 300mm f2.8 into a 420mm f4 (35mm equivalent 840mm f4.0) by just attaching the teleconverter inbetween the body and lens.
Claim £30 cash back until Saturday 31st January 2009 - more details here. Professional quality teleconverter which multiplies your lens' focal length by a .....