The compact and lightweight (5.6 oz, 160 g) Sigma APO Teleconverter 1.4x EX DG is a high-quality extender that preserves the image quality of the lens it's mounted to and multiplies its focal length by 1.4x without any variation in the minimum focusing distance. This teleconverter, equipped with a Pentax AF mount, features Sigma's new multi-layer coating to reduce flare and ghosting, which is a common problem with digital cameras. Sigma recommends using this teleconverter with their DG series lenses for best performance.
The teleconverter will cut back the amount of light by one f/stop. For example using a 1.4x teleconverter with a 300mm f/2.8 lens will effectively increase the focal length to approximately 420mm and the f/2.8 aperture will now be f/4. Teleconverters are best used with longer telephoto lenses and are not recommended for lenses wider than 50mm, e.g. 28-105mm (35mm format).
Note: This teleconverter will only fit and work with a select list of lenses. Please click here compatibility chart for compatible lens chart.