FOCUS, APERTURE & DEPTH OF FIELD

FOCUS, APERTURE & DEPTH OF FIELD
According to John Ingledew, in Photography, 2005, Portfolio Press:
"Focus is a tool of the photographer. When an object becomes clearly defined in the viewfinder it is described as being in focus or 'sharp'. If an object is not in focus it is described as being 'soft'. Choosing sharpness or softness can totally change a photograph. You have the choice to select which you wish to use by controlling the focus ring".

By turning the focus ring on the camera, the lens is moved backwards and forwards, which affects the point at which the light rays come together in the camera, which in turn makes the image go in and out of focus. You can make objects further away form the camera become the main focus with near distant objects out of focus and vice versa., and by setting the lens to the infinity setting you can make everything in the field of view in focus equally.

Alternatively, changing the aperture size will also affect the amount of light entering the camera and the radial effect on the image. This means that if aperture decreases in size - i.e.: the lens is stopped down for example to f22, then the more both the background and foreground will appear in focus. The opposite will occur when the lens is stopped up - to say f2.8, whereby the part of the scene which you want will be the only part in focus. f2.8 is the widest aperture and has the least DEPTH OF FIELD.