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A system is focal if an object ray parallel to the axis is conjugate to an image ray that intersects the optical axis. The intersection of the image ray with the optical axis is the focal point F ′ in image space. Focal systems also have an axial object point F such that any ray through F is conjugate to an image ray parallel to the optical axis.
The Ilford Manual of Photography is a comprehensive manual of photography, originally authored by C.H. Bothamley and first published in 1890 by The Britannia Works Company, which became Ilford, Limited in 1901. The 1890 edition was revised by Bothamley many times over a period of forty years until the first multi-authored edition, edited by ...
A principal focus or focal point is a special focus: For a lens , or a spherical or parabolic mirror , it is a point onto which collimated light parallel to the axis is focused. Since light can pass through a lens in either direction, a lens has two focal points – one on each side.
The rear focal length f ′ is the distance from the rear principal plane H ′ to the rear focal point F ′. Front focal distance (FFD) The front focal distance (FFD) (s F) is the distance from the front focal point of the system (F) to the vertex of the first optical surface (S 1). [1] [3] Some authors refer to this as "front focal length".
The points that span conjugate planes are called conjugate points. [ 3 ] For a thin lens or a curved mirror , 1 u + 1 v = 1 f , {\displaystyle {1 \over u}+{1 \over v}={1 \over f},} where u is the distance from the object to the center of the lens or mirror, v is the distance from the lens or mirror to the image, and f is the focal length of the ...
Diagram illustrating the flange focal length of an SLR–type and a mirrorless–type camera. For an interchangeable lens camera, the flange focal distance (FFD) (also known as the flange-to-film distance, flange focal depth, flange back distance (FBD), flange focal length (FFL), back focus [1] or register, depending on the usage and source) of a lens mount system is the distance from the ...
In differential geometry, conjugate points or focal points [1] [2] are, roughly, points that can almost be joined by a 1-parameter family of geodesics. For example, on a sphere, the north-pole and south-pole are connected by any meridian. Another viewpoint is that conjugate points tell when the geodesics fail to be length-minimizing.
Focal point may refer to: Focus (optics) Focus (geometry) Conjugate points, also called focal points; Focal point (game theory) Unicom Focal Point, a portfolio management software tool; Focal point review, a human resources process for employee evaluation; Focal Point, a 1976 studio album by McCoy Tyner "Focal Point: Mark of the Leaf", a Naruto ...