Wikipedia
Depth of focus is a lens optics concept that measures the tolerance of placement of the image plane (the film plane in a camera) in relation to the lens. In a camera, depth of focus indicates the tolerance of the film's displacement within the camera, and is therefore sometimes referred to as "lens-to-film tolerance."
In seismology, the depth of focus or focal depth refers to the depth at which an earthquake occurs. Earthquakes occurring at a depth of less than are classified as shallow-focus earthquakes, while those with a focal depth between and are commonly termed mid-focus or intermediate-depth earthquakes. In subduction zones, where older and colder oceanic crust descends beneath another tectonic plate, deep-focus earthquakes may occur at much greater depths in the mantle, ranging from up to .
The cause of deep-focus earthquakes is still not entirely understood since subducted lithosphere at that pressure and temperature regime should not exhibit brittle behavior. A possible mechanism for the generation of deep-focus earthquakes is faulting caused by olivine undergoing a phase transition into a spinel structure, with which they are believed to be associated. Earthquakes at this depth of focus typically occur at oceanic-continental convergent boundaries, along Wadati-Benioff zones.
Usage examples of "depth of focus".
It was not as thin as the illusions that Rutaro and his friends could produce, but a very workmanlike job to put all that depth of focus into a small package.
In short, the SEM recognized almost all of the one hundred and three elements, whether it was carbon, copper, or zinc, and because of the microscope's depth of focus, high resolution, and high magnification, trace evidence such as gunshot residue or the hairs on a marijuana leaf could be viewed in amazing, if not eerie, detail.
As he lowers his eyes from the walls of light, the mediated faces, he feels his contacts move, changing as they monitor his depth of focus.