Last time I used one I think it was a Hanimex 2x I had bought for pocket change at a camera fair, but I got what I paid for, and the resulting images had no sharpness, no contrast, no detail, no nothing of any quality. My lens was a 200mm f/4 SMC Takumar which is plenty nice when used normally, but the degradation was severe with the converter. I know that Pentax made converters for their K-mount lenses, but apparently none for their M42 lenses. My Takumar Lenses brochure does not list any. So has anyone ever found and used an M42 converter (2x or 3x) that doesn't suck?