Telephoto lens help

[Lemming51]

The 3x TC you are using is designed for much smaller lenses/sensors than the 2/3" sensor A200. There's nothing you can do about the vignetting, other than cropping the image later in editing.

The recommended TC for this model is Konica-Minolta's ACT-100 1.5x. If you want a higher power TC, make sure it's exit pupil (rearmost element) is close to the same diameter as the A200's lens.