Hi & welcome & all that.
I'm not a big user of long lenses, and this lens is generally quite well regarded. That said its probably not going to be as sharp as your Canon maco but a couple of general things to consider:
- Try some shots with the lens on a good quality tripod, preferably using a shutter realease. If you dont have a shutter realease, use the timer setting to eliminate camera shake when you press the button
- Consider using mirror lock up to further reduce vibrations
- What shutter speed are you using - when hand holding the general rule of thumb with 35mm film photography was to use a shutter speed at least 1/focal length. So for a 500mm lens you would need at least 1/500 sec. There is debate as to whether with the crop factor effectively increasing your focal lenght to 800mm you need to increase this to 1/800 sec
- Try stopping the lens down. Most lenses work best at least one stop down from the maximum aperture, if not two stops down so than means f9 - f13 at maximum zoom
Let us know how you get on