Sigma 824110 1.4x DG EX APO Teleconverter for Sigma SLR Cameras Review

Didn't actually use the teleconverter because it did not fit any of my lenses. I was in a hurry and just figured it would work with my Sigma 70-300mm DG, f4-5.6 --- or at least some of my other lenses such as the Pentax DA* 50-135mm f/2.8. NOT. Has a very limited set of compatible lenses; check on the Signma site (not listed on the Amazon site). I would have been shooting in bright sunlight, so was not concerned with the loss of a stop.
On the plus side, Amazon was great. Paid for return postage and quickly credited my purchase.

Buy it here now!