Narrow DOF (Depth of Field)

Depth of field shows the range of a shape and clear image. By adjusting the aperture and focus everything in the front and the rear of the image starts to lose its sharpness. 

 

Wide angel lenses are better at creating DOF (Depth of field) than Telephoto lenses as with a wide angle you can get the subject in the image and the foreground and surrounding objects etc. By adjusting your settings you can achieve DOF on the subject matter and the rest is out of focus. 

Setting the aperture at a large aperture so that you are letting in more light gives more Depth of field & the closer the subject the better.

In this picture the dragonfly has been the subject of focus and the grass has been out of focus surrounding it making you look only at the Dragonfly.

 

This chart shows the focal point and circles of confusion, this is the light coming from the object to the cameras sensor to create the DOF.The light in this diagram shows the circle of confusion where by the amount of light let in by the aperture and hitting the cameras sensor will make the object in focus however if they hit the sensor slightly out then the subject could be out of focus. Getting the balance right by setting the aperture and the lens length right.

To get a wide DOF you would be aiming to get the whole subject in focus by using a smaller aperture F.22  as you would need less light but your lens would be aiming further away and the shutter speed would be slower around 1/30^th of  a second without a tripod if possible.