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The pupil of the human eye can range in size from 2 mm to over 8 mm to adapt to the environment. The human eye can detect a luminance from 10 −6 cd/m 2, or one millionth (0.000001) of a candela per square meter to 10 8 cd/m 2 or one hundred million (100,000,000) candelas per square meter.
The pupil magnification is used in calculations of the effective f-number, which affects a number of important elements related to optics, such as exposure, diffraction, and depth of field. For all symmetric lenses, and for many conventional photographic lenses , the pupils appear the same size and so the pupil magnification is approximately 1.
The pupil gets wider in the dark and narrower in light. When narrow, the diameter be 1.5 to 4 millimeters. [4] In the dark it will be the same at first, but will approach the maximum distance for a wide pupil 3 to 8 mm. [4] However, in any human age group there is considerable variation in maximal pupil size. For example, at the peak age of 15 ...
The iris controls the size of the pupil by means of contracting the iris sphincter muscle and/or the iris dilator muscle. The size of the pupils is dependent on many factors (including light, emotional state, cognitive load, arousal, stimulation), and can range from less than 2 mm in diameter, to as large as 9 mm in diameter.
The entrance pupil is typically about 4 mm in diameter, although it can range from as narrow as 2 mm (f /8.3) in diameter in a brightly lit place to 8 mm (f /2.1) in the dark as part of adaptation. In rare cases in some individuals are able to dilate their pupils even beyond 8 mm (in scotopic lighting, close to the physical limit of the iris.
The entrance pupil is the image of the aperture stop viewed from the front of the optical system and here it is a virtual image. Chief rays and marginal rays determine the location and the size of the entrance pupil, respectively. A camera lens adjusted for large and small aperture. The visible opening is the entrance pupil of the lens.
The Neurological Pupil index, or NPi, is an algorithm developed by NeurOptics, Inc., that removes subjectivity from the pupillary evaluation. A patient's pupil measurement (including variables such as size, latency, constriction velocity, dilation velocity, etc.) is obtained using a pupillometer, and the measurement is compared against a normative model of pupil reaction to light and ...
A manual pupillometer measures pupil size via a comparison chart method. There are several types of manual pupillometers. The most common type is the Haab scale, or Haab's pupillometer, which is a series of graduated filled circles on a slide ruler. [2]