Bokeh / Background Blur Calculator

How It Works

Background blur (bokeh) is determined by the physical size of the blur circles on the sensor. Larger blur circles mean more background separation. Three factors increase blur: wider aperture (lower f-number), longer focal length, and greater distance between subject and background. The entrance pupil (focal length divided by f-number) is a useful shortcut for comparing blur potential across lenses. An 85mm f/1.4 has a 61mm entrance pupil versus 36mm for a 50mm f/1.4.