You can make very sharp images with the 2X and that particular lens Do you have the IS version? Either way it should be mounted on a tripod for best results Your effective focal length is 780 Having a shutter speed of 1/500 your really need to be steady !!!
Try shooting at a newspaper with the tripod head locked and check !!!
Thanks...but I have Is version and I used a tripod ...also if not excellent.
Could better, I think, use the remote switch...or I am not hight sensibility on the moment of shhot...