The Panasonic TC20E 2X Teleconverter is an accessory designed specifically for telephoto lenses with a focal length range of 200mm to 50-200mm. A teleconverter is an optical device that increases the effective focal length of a lens, allowing you to magnify the image and bring distant subjects closer. In the case of the Panasonic TC20E, it doubles the focal length of the lens it is attached to.

The teleconverter is compatible with Panasonic lenses that have a Micro Four Thirds mount, which is a standard used by Panasonic and Olympus for their mirrorless interchangeable lens cameras. By attaching the TC20E 2X Teleconverter to your lens, you can effectively achieve double the focal length without sacrificing image quality.

It is important to note that using a teleconverter reduces the amount of light entering the lens, effectively increasing the f-number (aperture value) by two stops. This means that if you attach the TC20E to a lens with a maximum aperture of f/2.8, the effective maximum aperture will become f/5.6. This reduction in aperture may affect autofocus performance, especially in low-light conditions.

Additionally, teleconverters can have a slight impact on image quality, including a potential loss of sharpness and increased susceptibility to lens aberrations. However, the Panasonic TC20E is designed to minimize these effects and maintain high image quality when used with compatible lenses.

Overall, the Panasonic TC20E 2X Teleconverter is a useful accessory for photographers who require extended reach for capturing distant subjects, particularly in wildlife, sports, or other telephoto applications.