Sigma has announced two new teleconverters for Sony mount tele-photo lenses--the APO Teleconverter 1.4x EX DG and the APO Teleconverter 2x EX DG.
The two new teleconverters are designed to work with fast-focusing HSM (hyper sonic motor) lenses; they are HSM-capable and are able to maintain the HSM's fast focusing speeds. Any lens used with the teleconverters must be a fast lens, f2.8 or higher, to make use of the teleconverter. If a non-HSM lens is used, focus is manual only, the autofocus will not work. Both teleconverters employ Sigma's Super Multi Layer coatings to reduce flare and ghosting.
Teleconverters go between the lens and the camera body, extending the len's focal length. They are for use with fast telephoto lenses, and are a favorite with wildlife and nature photographers. A 1.4x teleconverter extends the focal length by 1.4x, so a 200mm lens acts like a 280mm lens. A 2x teleconverter extends the focal length by 2x, so 200mm lens acts like a 400mm.
No pricing or availability information is available yet.