I tried a lot to take portrait pictures with blur background using my FujiFilm HS10 but haven't succeeded yet. I use f2.8 but still cannot get the effect. Can any of the experts give me any suggestion.
It may help to realize that depth of field depends in part on the distance to the subject. Even at large apertures (low numbers like f/2.8), the depth of field will be much greater if you focus on something far away than if your subject is close to the camera.
So, if your goal is a portrait with a soft background, get relatively close to the subject and use a large aperture like the f/2.8 setting that you're trying. If you want the background to be very blurry, increase the distance between subject and background.