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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.
where L′ is the scotopic luminance in cd m −2 and p is pupil area in mm 2. Although named "retinal illuminance" (and originally named "photon" by Troland), trolands do not measure the actual photon flux incident on the retina; that quantity depends on the specific wavelengths of light that constitute the luminance used in the calculation.
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 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 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 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 more difficult the task, the greater pupil diameter observed from the time preceding the solution [58] until the task was completed. [59] While these discoveries from the 1960s sparked renewed interest in the psychological significance of pupil size, research had substantially earlier identified the relationship between pupil size and effort.