One of the popular photo looks these days is the soft focus look; and for many photographers it's tough to get just right unless you really understand what's going on. The soft focus look is based on a look that photographers used to produce years ago in the film days.
Some photographers achieved the look by putting stockings over the front of the lens or rubbing vaseline on a piece of glass then putting that in front of the lens. Other photographers do it by scratching a lens up a whole lot to kill the sharpness and details that it can produce. . thephoblographer.com