The Pentax SMC-A 2x L Rear Converter (also known as a tele-extender) is designed to fit on select Pentax 35mm "long" lenses. The converter will multiply the focal length of the existing lens by 2x, and will cut back the amount of light by 2 f/stops. For example, using a 2x teleconverter with a 300mm lens will effectively increase the focal length to 600mm. A lens set to f/2.8 will now be f/5.6.
Note: Due to the high-quality design of this converter (6 elements/5 groups), the teleconverter will only fit and work with a select range of lenses. Only the following lenses are compatible:
(*) Note: Fits, but better performance can be achieved with other versions.