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Angular field of view is typically specified in degrees, while linear field of view is a ratio of lengths. For example, binoculars with a 5.8 degree (angular) field of view might be advertised as having a (linear) field of view of 102 mm per meter. As long as the FOV is less than about 10 degrees or so, the following approximation formulas ...
Because their images have constant magnification and constant viewing angle across the field of view, object-space telecentric lenses are used for metrology applications, where a machine vision system must determine the precise size and shape of objects independently from their exact distance and position within the field of view.
The hyperfocal distance has a property called "consecutive depths of field", where a lens focused at an object whose distance from the lens is at the hyperfocal distance H will hold a depth of field from H/2 to infinity, if the lens is focused to H/2, the depth of field will be from H/3 to H; if the lens is then focused to H/3, the depth of ...
With increasing magnification, the depth of field – the distance between the nearest and the farthest objects that are in acceptably sharp focus in an image – decreases. The depth of field reduces quadratic with the magnification, so compared to 7× binoculars, 10× binoculars offer about half (7² ÷ 10² = 0.49) the depth of field.
The eye relief of an optical instrument (such as a telescope, a microscope, or binoculars) is the distance from the last surface of an eyepiece within which the user's eye can obtain the full viewing angle. If a viewer's eye is outside this distance, a reduced field of view will be obtained.
The image on the right has the same apparent field of view as the center eyepiece but has a shorter focal length, giving the same true field of view as the left image but at higher magnification. The Plössl, an eyepiece with a large apparent field of view
For example, with a magnification ratio of 1:2, we find = and thus the angle of view is reduced by 33% compared to focusing on a distant object with the same lens. Angle of view can also be determined using FOV tables or paper or software lens calculators.
The field of view requires the magnification, which is formulated by its division over the apparent field of view: = = =. The resulting true field of view is 0.64°, not allowing an object such as the Orion nebula , which appears elliptical with an angular diameter of 65 × 60 arcminutes , to be viewable through the telescope in its entirety ...