Digital Photography in Available Light

creative controls

Focus

The word ‘focus’ refers to either the point or plane at which an image is sharp or the ‘centre of
interest’. When an image is being framed the lens is focused on the subject which is of primary
interest to the photographer. The viewer of an image is instinctively drawn to this point of focus or
the area of the image which is the most sharp. This becomes the ‘focal point’ of the image. In this
way the photographer guides or infl uences the viewer to not only look at the same point of focus
but also share the same point of interest.

Lens controls

Limitations of focus
When an object is made sharp by focusing the lens all other subjects at the same distance are
equally sharp. Subjects nearer or further away are progressively less sharp.
On DSLR cameras the focusing ring on the lens can be rotated between two stops at which point
it can no longer be turned to alter focus. As the subject moves closer to the lens a distance is
reached where the subject can no longer be focused. The focusing ring will not turn further and
reaches its stop (no stops may be present on the focusing ring of a prosumer digicam). This
represents the ‘closest point of focus’. As the subject moves further away the focusing ring
again reaches a point where it will not turn further. This distance is called ‘infi nity’ on the lens
and is represented by the symbol ∞. At increasing distances from the camera the subject will
continue to remain in focus. The closest point of focus and the point of infi nity changes between
different lenses. Prosumer digicams usually offer manual focusing as an option, but the absence
of stops can make the process a little more time consuming.

ACTIVITY 1

Record the closest focusing distance of all your lenses. If you have a zoom lens check the

closest focusing distance at the shortest and longest focal length.

Without using the macro mode or option of a prosumer digicam take two creatively designed

images using the closest focusing distance of your lens.

Focus ring

Depth of fi eld scale

Aperture ring