focal length

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length

 [length]
an expression of the longest dimension of an object, or of the measurement between its two ends.
crown-heel length (CHL) the distance from the crown of the head to the heel in embryos, fetuses, and infants; the equivalent of standing height in older persons.
Measuring an infant's crown-heel length. From Lammon et al., 1996.
crown-rump length (CRL) the distance from the crown of the head to the breech in embryos, fetuses, and infants; the equivalent of sitting height in older subjects.
cycle length in cardiac pacing terminology, the time interval in milliseconds from one event to the next; it is the inverse of the intrinsic rate (beats per minute) or the paced rate (pulses per minute).
focal length the distance between a lens and an object from which all rays of light are brought to a focus.

focal length

In optics, the length from the lens to the point of focus of light rays passing through the lens.
See also: length

length, focal

The linear distance separating the principal focal point (or focus) of an optical system from a point of reference (e.g. vertex, principal point, nodal point). The first (anterior) focal length is the distance from the lens (or first principal point) to the first principal focus. The second (posterior) focal length is the distance from the lens (or second principal point) to the second principal focus. Symbol: f.In a spherical mirror the focal length f, i.e. the distance between the focal point and the pole of the mirror, is equal to half its radius of curvature r
f
= r/2Syn. focal distance. See principal focus; mirror; cardinal points; principal points; equivalent power; refractive power; sign convention.

focal

1. limited to a small area or volume.
2. pertaining to or emanating from focus.

focal distance
see focal-film distance.
focal length
the distance between the lens and an object from which all rays of light are brought to a focus.
focal liver disease
widely disseminated micro-abscesses or abscesses, migration paths of helminth larvae.
focal macular melanosis
dark colored spots on the skin, not elevated above the skin surface but apt to be confused with melanosis.
focal myelitis-encephalitis
widely disseminated inflammatory lesions, usually the result of blood-borne infection, in brain and spinal cord.
focal symmetrical encephalomalacia
see focal symmetrical encephalomalacia.
focal symmetrical spinal poliomalacia
see focal symmetrical spinal poliomalacia.
focal ulcerative dermatitis
manifest by ulcers in the unfeathered anterior breast skin of 4 to 5 months old male turkeys. The incidence is influenced by litter type. Called also breast buttons.
focal zone
in ultrasound, the area of the transducer where the sound beam is most sharply focussed and where the area under examination will give the best image.
References in periodicals archive ?
But as recently as 20 years ago the standard lens supplied with a 35mm camera had a fixed focal length of 50mm, which captured the scene being photographed pretty much as the eye saw it.
To reduce error that may result from using two specimens, mean measurements of focal length for each eye type were used, thereby accounting for possible differences in focal lengths between the two specimens.
On-location news coverage can frequently involve rapid changes in subject distance and associated focal length.
It is equipped with a high-performance 20x optical zoom (up to 40x*1 when Dynamic Fine Zoom is used) NIKKOR lens that covers the wide-angle 25 mm to super-telephoto 500 mm angles of view (equivalent focal lengths in 35mm 135 format), as well as 4-axis Hybrid VR (vibration reduction) .
1-million pixels*, and is equipped with a 5x optical zoom NIKKOR lens that covers a broad range of focal lengths, from the wide-angle 26mm to the telephoto 130mm (equivalent angles of view in 35mm 135 format).
8 R LM WR is a flagship XF standard zoom lens with a focal length equivalent to 24mm 84mm (in 35mm format equivalent), and a constant F2.
5B and YJ13x6B Series 2/3-Inch SD Lenses Feature Widest Focal Lengths, Highest Zoom Ratios, Fastest Zoom Speeds, IFpro Technology, Shuttle Shot, and More
Despite being equipped with a 60x (up to 120 with Dynamic Fine Zoom) optical zoom NIKKOR lens offering the highest zoom ratio in COOLPIX history with coverage of a broad range of angles of view, from the wide-angle 24mm to super-telephoto 1440mm (equivalent focal lengths in 35mm 135 format), the P600 is very compact.
We have worked with our top customers to develop a useful set of focal lengths for many applications.
0-million pixels, a 12x optical zoom NIKKOR lens that covers the wide-angle 25mm to 300mm range of angles of view (equivalent focal lengths in 35mm 135 format), Dynamic Fine Zoom, which supports digital zoom up to 24x without compromising the high-resolution, and a Wi-FiA function that enables simple connection to smart devices, have been packed.
Mounted on the PENTAX *ist D or PENTAX *ist DS, this lens offers focal lengths equivalent from 76.
8G ED responds to a variety of needs by enriching our fast prime lens lineup covering focal lengths from wide-angle to the mid-telephoto range.