DEPTH OF FIELD
The depth of field is the zone within which the subject forms an image that is within the depth of focus. Anything within the depth of field will appear as sharp a if it were in focus. Features of Depth of Field
- Larger F Numbers give greater depth of field.
- Shorter Focal Lengths give greater depth of field.
- Greater subject distances give greater depth of field.
- Depth of field is greater behind the subject than in front.
The more that the lens is stepped down, the greater the depth of field. The lens aperture does more than just control the amount of light. It has the second important function of controlling the depth of field.
If the Focal Length is changed, the depth of field also changes, decreasing toward the telephone direction.
Since a wide-angle lens has a great depth of field it can give both a sharp foreground and a sharp background. A telephoto lens disregards the background completely and emphasizes only the subject matter it is focused on.
In other words, if lighting and subject distance is the same, a shorter focal length will give greater depth of field. Therefore, a 3.5mm lens is greater that a 6mm to 12mm to a 28mm.