Introduction of Depth Of Field (DOF).

Depth of Field (DOF) means depth. in the field of photography, DOF is technically means that the variation range or distance between the camera and the subject of the image to produce variations in the sharpness (focus) the picture can still be accepted (no blur). so, DOF is used to indicate a specific room in the photos that get special attention by eye because of differences in sharpness (focus).

Depth Of Field is influenced by 3 things, namely:
1. Distance from the main focus of the camera.
Wide space with a sharp straight proportionate square distance objects. If we change the distance between the camera and the object of 3x (more friction with the camera back from the original position) the width of space will be a sharp 9x original width.
2. Aperture diaphragm
Wide space with a sharp straight proportionate diaphragm. Example: if the diaphragm was 2 stop of f / 8 to f/16, so wide space will be a sharp 2x original width.
3. Focal length lens is used.
Wide space sharply inverted proportionate length of the focus square. In other words, the wide space will be a sharp 4x wide-back if we change the lens from 50mm to 100mm (focal length lens half of the original).
The wide angle lens then the wide area space sharpness. This means, when the camera is in zoom-out, shoot the object that we will be more free to move forward or backward within a specified distance from the camera and still look sharp / focus. Sharp narrow space in the telephoto image, also called narrow DoF, while striking a wide space in the image is also wide DoF wide.

The more open the diaphragm, the more narrow the space sharpness. This means, set the focus in situations that are less lighting would be more problematic as the diaphragm must be opened wide and the object will not be free to move near or far from the camera as it would be out of focus (out of focus).

The combination of telephoto (zoom in all the way) and the diaphragm is wide open, will result in a sharp narrow space. One example, when taking telephoto pictures (tight shot) a singer who perform a concert at night with minimal lighting, we must carefully manage the focus, because only a few performers are moving near or far from the camera, then he will be easy to out of focus.