The closer the object to you, and the farther the distance from the subject to the background, the greater the blur will be... So generally speaking, the closer you get to the subject, the more blur...Thanks for those useful links. I am getting good results now, but how to do it when the object is very close? For e.g. when taking out shots from 5 feets away.
I disagree, if you change the aperture you don't change what the sensor sees, if you change the focal length, you change what the lens sees... You get a completely different picture, rather than just selective blur, which is what you get by widening the aperture.
The closer the object to you, and the farther the distance from the subject to the background, the greater the blur will be... So generally speaking, the closer you get to the subject, the more blur...