Beautifully blurry backgrounds can make for great shots.
Your attention is drawn to what is sharply in focus, helping tell the story of what your photo is about.
With enough blur the image becomes simpler and your composition becomes one subject and a number of blocks of colour or tone.
- Technical jargon: That out-of-focus blur is called bokeh. The amount of the image in focus is called depth of field.
How to get a Shallow Depth of Field
Your depth of field depends on your aperture and distance from the subject. Both wider apertures (smaller F-stop numbers) and being closer to the subject (which can be achieved by either standing closer or by using a telephoto or macro lens) give you a narrower depth of field.
If you want to get really technical, here is a depth of field calculator: DOF
In this photo of a grasshopper I used an extension tube to turn my lens into a macro lens by letting it focus closer. The grasshopper was pretty cooperative by sitting still and staring at me (unlike the really unhelpful ladybirds on my sunflowers - next shot - which would not keep still!). I focused on the eyes which is where we naturally look first. The colourful background was created by a pretty garden windmill, turned into big blocks of colour by bokeh.
