Hi Anirban

. . . . What lens and Camera could had been used. . . .

That camera does not matter, any dgital SLR or a compact with manual control and a good zoom can do this.

However the lens does matter - the longer the lens, ie medium to long telephoto, the more easily it can be achieved.

The important thing is to set the depth of field very shallow ie high shutter speed, wide aperture and focus on the subject.

There is a lot of dependancy on the lens quality - more information here

HTH

John EB