Bokah or Blurred Background

Bokah -- This word has its origin in the Japanese word boke or blur.  It refers to the out-of-focus areas in a photograph as a result of the opening in the aperture. 

A small f/stop means you have a wide aperture in the opening of the lens.  That wide opening causes a shallow depth-of-field or area in focus.  f/1.4 is a wide opening but f/22 is a small opening.  (Small number = small depth-of-field.  Big number = big depth-of-field.)

A small change in the f/stop causes a change in the area in focus.  That small change results in a very different bokah.  

Every lens has it's own bokah. Some lenses are known for their "sweet" bokah.  

Note that the distance between subject and background also have an impact on bokah.  The greater the distance between subject and background, the greater the possibility of softening the background.  I like to work with 8 or 10 feet when trying to get a nice bokah.  

A nice soft background comes with a wide angle lens as well as a telephoto lens.  Put your lenses to the test.