Frequent dilemma, particulary when using Sigma lenses is whether should we use Sigma or Kenko teleconverters. Another frequent question is how much pic quality deterioration can we expect when using TCs. Here I have tested both Kenko Pro 300 DG and both Sigma EX TCs. Chromatic abberation is multiplied by 10 in order to be seen well. The test bed was Nikon D70 and Sigma 150 mm f/2.8 EX Macro lens that displays pretty good characteristics (shown as well, without any TC).