Sigma 1.4x EX DG Tele Converter Review
The Sigma 1.4x EX DG Tele Converter offers build quality similar to the more professional lineup, Sigma EX. It should be noted that this teleconverter work with only Sigma lenses. Lightweight and relatively compact, the teleconverter can add longer focal-length to standard Sigma lenses.
There are about a dozen of compatible lenses to choose from, but not all have built-in autofocus function. Image quality generated by this teleconverter is generally good, although images may lose a bit of sharpness and contrast. It is equipped with multi-layer coating to reduce ghosting and flare, which plague many digital cameras.