Sigma 1.4X APO Tele Converter for Canon-AF Camera

Rating:
Summary: Bargain alternative to Canon's 1.4x Teleconverter?
Review: The Sigma APO teleconverter is a little more than half the price of the Canon teleconverter, and it boasts an APO element to reduce chromatic aberration. I've found this teleconverter to be reasonably sharp, but there is noticeable vignetting when I use it with my Canon 300mm f4. Sigma claims that the teleconverter is designed to be matched with their high-end tlelphoto lenses, and perhaps this is the case. However, I wasn't very satisfied with the performance of this teleconverter.

Rating:
Summary: Bargain alternative to Canon's 1.4x Teleconverter?
Review: The Sigma APO teleconverter is a little more than half the price of the Canon teleconverter, and it boasts an APO element to reduce chromatic aberration. I've found this teleconverter to be reasonably sharp, but there is noticeable vignetting when I use it with my Canon 300mm f4. Sigma claims that the teleconverter is designed to be matched with their high-end tlelphoto lenses, and perhaps this is the case. However, I wasn't very satisfied with the performance of this teleconverter.