May 6 2014
Depth of focus in optics is a measure of the tolerance of the placement of the image plane with respect to the lens. In photography, depth of focus refers to the tolerance of the film's displacement within the camera. Depth of focus is also referred to as the lens-to-film tolerance.
Depth of focus pertains to the image space. It varies with the aperture and the magnification of the objective lens.
Depth of focus assumes importance in the field of photomicrography. The film used in photomicrography must be illuminated in a plane that falls within the focus region. The value of depth of focus is obtained from the value of the f-number of the lens, image distance, and the circle of confusion.
Difference between Depth of Focus and Depth of Field
Depth of focus is the distance over which the image plane can be displaced, with the object plane being maintained under sharp focus. Depth of field, on the other hand, is the range of distances within the object space for which the image is of acceptable sharpness.
Depth of focus is measured in terms of microscopic units, while depth of field is measured in terms of macroscopic units.
Factors that Influence the Depth of Focus
The factors that influence the depth of focus of the lens are listed below:-
- Format – Depth of focus for small-format cameras is relatively diminutive
- Lens calibration – In motion pictures, the combination of the lenses and the camera gate influences the depth of focus
The factors that affect depth of field have a different effect on the depth of focus.
References