Sharp enough for me. An Olympus 40-150mm lens and that teleconverter. Think the newer teleconverters attach to the back. They don’t make one for that lens. Cheaper to buy that old teleconverter, then a new lens. Just needed a step down adapter too.
Also, use a tripod. My camera does have IBIS, but not good enough for me. Also, what is the lens focal length supposed to be with an old teleconverter for the IBIS?