In every photo there'll be a range around the chosen focus distance that appears to be sharp. This range is called the "Depth-of-Field". The following slide show demonstrates the effect of different aperture
settings regarding the depth-of-field within a
scene. The lamp is the point of focus here. Select one of the shown aperture
settings and observe the effect on the background (the castle) - requires
The depth-of-field is dependent on the OBJECT MAGNIFICATION ON THE FILM and
the chosen aperture at a specific focal length. At theoretical f/1.0 the DOF
is the same for all focal length and the same object magnification. However,
stopping down changes the DOF differently depending on the focal length. The increase
of DOF is bigger towards shorter focus distances.
Whatever aperture you choose - the sharpest point is located at the chosen focus distance.
The sharpness around it will deterioate more or less rapidly dependent on the distance from
the focus plane and the chosen aperture.
The larger area of the Depth-of-Field will be in rear of the focus point (see picture).
It is possible to calculate the Depth-of-Field based on a defined sharpness. Every point outside the focus plane
isn't a point but a circle. If this circle is minimal up to a certain standard a plane in the field will appear sharp.
This minimal circle or "Error"-level is known as the "Circle-of-confusion". The Java-Applet below offers 4 different circles
for different needs.
- 0.03mm (circle-diameter) represents the common standard which is usable for small prints or low-end needs
- 0.025mm - for posters
- 0.02mm - professional level (also for slides)
- 0.01mm - this level is oriented at the resultion of an average film or lens (about 100 lines/mm=0.01mm). The calculated
Depth-of-Field will be sharp by any standard !
The Applet will also calc the "Hyperfocal-Distance" represented by the first focus point where the Depth of Field covers
the area between 1/2 of the H.-Distance up to infinity.
The starting process of the JAVA applet may take a few moments so please be patient!