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  • diameter of the pupil
  • By moving the card closer to or further away from the eyepiece, the disc of light will be minimized when the card is at the exit pupil, and the bright disc then shows the diameter of the pupil. (wikipedia.org)
  • The ipRGCs have other functions as well, such as signaling the need for changing the diameter of the pupil in changing light conditions. (wikipedia.org)
  • Play media The pupillary light reflex (PLR) or photopupillary reflex is a reflex that controls the diameter of the pupil, in response to the intensity (luminance) of light that falls on the retinal ganglion cells of the retina in the back of the eye, thereby assisting in adaptation to various levels of lightness/darkness. (wikipedia.org)
  • Optic
  • Larger stops can cause the intensity reaching the film or detector to fall off toward the edges of the picture, especially when, for off-axis points, a different stop becomes the aperture stop by virtue of cutting off more light than did the stop that was the aperture stop on the optic axis. (wikipedia.org)
  • lens
  • An off-axis pupil and the principle of chromatic aberration (where different wavelengths come to focus at different distances behind a lens) can combine to provide "color-blind" animals with a way to distinguish colors. (pnas.org)
  • Cataract cannot usually be seen on casual inspection because it is happening in the lens which is just behind the iris and the pupil aperture. (everything2.com)
  • A simple cosmetic solution is a specialized cosmetic contact lens with an artificial pupil aperture. (wikipedia.org)
  • For a pupil size of ≥ 3 mm, distinctive MTF peaks were observed for all lenses: two peaks for the extended depth of focus and bifocal lenses with +1.75 and +4.00 diopters (D) addition, respectively, and three peaks for the trifocal lens with +1.75 and +3.50 addition for intermediate and near vision, respectively. (escrs.org)
  • For small pupil apertures, the MTF peaks for the far and intermediate focal distances of the trifocal and extended depth of focus lenses overlap, but the trifocal lens presented an additional MTF peak for the near focal points. (escrs.org)
  • For example, in a telescope, the aperture stop is typically the edges of the objective lens or mirror (or of the mount that holds it). (wikipedia.org)
  • In addition to an aperture stop, a photographic lens may have one or more field stops, which limit the system's field of view. (wikipedia.org)
  • In that case, the exit pupil can be easily calculated as the diameter of the objective lens divided by the magnification. (wikipedia.org)
  • The centre of the diaphragm's aperture coincides with the optical axis of the lens system. (wikipedia.org)
  • A lens that is focused onto the point source will have optics that change the spherical wave front into a planar wave before it passes through the pupil or aperture stop. (wikipedia.org)
  • These two strata are continuous with each other at the cup margin, which ultimately overlaps the front of the lens and reaches as far forward as the future aperture of the pupil. (wikipedia.org)
  • diameters
  • Multifocal and monofocal IOLs were compared evaluating the Visual Information Fidelity (V.I.F.) criterion and the quality of different images at different pupil diameters. (escrs.org)
  • V.I.F. values and quality of image of distant focus were lower for multifocal IOLs than monofocal IOLs at all tested pupil diameters. (escrs.org)
  • V.I.F. and image quality of near focus were higher for multifocal than monofocal IOLs at all pupil diameters. (escrs.org)
  • This corresponds to a decrease of the pupil and aperture diameters by a factor of 1/ 2 {\displaystyle \scriptstyle {\sqrt {2}}} or about 0.7071, and hence a halving of the area of the pupil. (wikipedia.org)
  • large-pupil
  • An astronomical telescope requires a large pupil because it is designed to be used for looking at dim objects at night, while a microscope will require a much smaller pupil since the object will be brightly illuminated. (wikipedia.org)
  • thus
  • The aperture also determines how many of the incoming rays are actually admitted and thus how much light reaches the image plane (the narrower the aperture, the darker the image for a given exposure time). (wikipedia.org)
  • The location of the exit pupil thus determines the eye relief of an eyepiece. (wikipedia.org)
  • It is thus possible to deduce the point-spread function of the out of focus point source as the Fourier transform of the pupil function. (wikipedia.org)
  • brightness
  • The aperture stop is the aperture setting that limits the brightness of the image by restricting the input pupil size, while a field stop is a stop intended to cut out light that would be outside the desired field of view and might cause flare or other problems if not stopped. (wikipedia.org)
  • In general, these structures are called stops,[citation needed] and the aperture stop is the stop that primarily determines the ray cone angle and brightness at the image point. (wikipedia.org)
  • corresponds
  • This modulation corresponds to a change in complex argument of the pupil function of such an imaging device, and it can be engineered with different goals in mind: e.g. extending the depth of focus. (wikipedia.org)
  • typically
  • The maximum pupil size of a human eye is typically 5-9 mm for individuals below 25 years old, and decreases slowly with age as shown as an approximate guide in the table below. (wikipedia.org)
  • dilate
  • Many fish have neither, and, as a result, their irides are unable to dilate and contract, so that the pupil always remains of a fixed size. (wikipedia.org)
  • Furthermore, the pupil will dilate if a person sees an object of interest. (wikipedia.org)
  • passes
  • The size and shape of this disc is crucial to the instrument's performance, because the observer's eye can see light only if it passes through this tiny aperture. (wikipedia.org)
  • refers
  • In some contexts, especially in photography and astronomy, aperture refers to the diameter of the aperture stop rather than the physical stop or the opening itself. (wikipedia.org)
  • In contrast, the terms direct and consensual refers to the side where the light source comes from, relative to the side of the reacting pupil. (wikipedia.org)
  • displaystyle
  • The light may also be attenuated differently at different positions ( u , v ) {\displaystyle (u,v)} in the pupil, sometimes deliberately for the purpose of apodization. (wikipedia.org)
  • Such change in amplitude of the light wave is described by the factor A ( u , v ) {\displaystyle \mathrm {A} (u,v)} . The pupil function is also directly related to the point spread function by its Fourier transform. (wikipedia.org)
  • R , {\displaystyle \mathrm {P} (u,v)=0,\forall u,v:{\sqrt {u^{2}+v^{2}}}>R,} where R {\displaystyle R} is the pupil radius. (wikipedia.org)
  • light rays
  • A clear vial of milky fluid can also be used to visualize the light rays, which appear as an hourglass shape converging and diverging as they exit the eyepiece, with the smallest cross-section (the waist of the hourglass shape) representing the exit pupil. (wikipedia.org)
  • It appears black because light rays entering the pupil are either absorbed by the tissues inside the eye directly, or absorbed after diffuse reflections within the eye that mostly miss exiting the narrow pupil. (wikipedia.org)
  • limits
  • in practice these conditions may not be realized, and the images projected by uncorrected systems are, in general, ill-defined and often completely blurred, if the aperture or field of view exceeds certain limits. (wikipedia.org)
  • image
  • The bizarre off-axis pupils of these animals can be understood as an adaptation that maximizes spectral information, even at the expense of image acuity. (pnas.org)
  • V.I.F. and image quality of distance focus produced by a multifocal IOL are lower at any given pupil aperture when compared to monofocal IOL. (escrs.org)
  • The aperture determines how collimated the admitted rays are, which is of great importance for the appearance at the image plane. (wikipedia.org)
  • If an aperture is wide, then highly collimated rays are admitted, resulting in a sharp focus at the image plane. (wikipedia.org)
  • This means that a narrow aperture results in an image that is sharp for things at the correct distance. (wikipedia.org)
  • radius
  • Posters and online campaigns promoting the search for Madeleine use the word "Look" with the first "O" in the word being drawn in the shape of a coloboma radius extending from the pupil at the 7 o'clock position. (wikipedia.org)
  • considerable
  • At intermediate distance V.I.F. values of multifocal IOLs showed a slight increase compared with the monofocal at 6.1 mm pupil diameter and considerable improvement at 2.6 mm. (escrs.org)
  • larger
  • Therefore, to have the same exposure at this larger aperture as at the previous aperture, the shutter would be opened for half as long (i.e., twice the speed). (wikipedia.org)
  • determines
  • The distance of the exit pupil from the sensor plane determines the range of angles of incidence that light will make with the sensor. (wikipedia.org)
  • system
  • The word aperture is also used in other contexts to indicate a system which blocks off light outside a certain region. (wikipedia.org)
  • In the case of an incoherent optical imaging system, the optical transfer function is the auto correlation of the pupil function. (wikipedia.org)
  • The pupil function of such an ideal system is equal to one at every point within the pupil, and zero out with it. (wikipedia.org)
  • Distance
  • In the dark it will be the same at first, but will approach the maximum distance for a wide pupil 3 to 8 mm. (wikipedia.org)
  • occasional
  • An early, 18th century school, located three miles west of Morristown was described as follows: "The building was constructed of logs, and instead of glass window, sheep skins were stretched over apertures made by sawing off an occasional log. (wikipedia.org)
  • high
  • Available with high-numerical-aperture and oil-immersion options, they are suited for bright-field, dark-field, differential interference contrast, fluorescence and polarization microscopy. (photonics.com)
  • known
  • The traditional British boarding school system, known as fagging, where junior pupils became personal servants to the senior boys was officially abolished in the 1920s, and Marlborough was one of the first public schools to do so. (wikipedia.org)
  • At this stage the pupils do not remain completely still, therefore may lead to oscillation, which may intensify and become known as hippus. (wikipedia.org)
  • large
  • Several types of colonic irrigation is done by using enema for injecting water, at times coalesced with herb forms or some liquid inside the large intestines through the rectal aperture deploying specialized equipments. (enlisthealthguide.com)
  • example
  • For example, at the peak age of 15, the dark-adapted pupil can vary from 4 mm to 9 mm with different individuals. (wikipedia.org)
  • term
  • For the academic year 2015/16, Marlborough charged £9,610 per term for day pupils, making it the most expensive day school in the Headmasters' and Headmistresses' Conference (HMC) - the association of British independent schools. (wikipedia.org)
  • An anomaly of etymology is that in a surprising number of unrelated languages the meaning of the term for pupil is little person. (wikipedia.org)
  • Another term for the constriction of the pupil is miosis. (wikipedia.org)
  • cause
  • The dilator pupillae, innervated by sympathetic nerves from the superior cervical ganglion, cause the pupil to dilate when they contract. (wikipedia.org)
  • If the drug pilocarpine is administered, the pupils will constrict and accommodation is increased due to the parasympathetic action on the circular muscle fibers, conversely, atropine will cause paralysis of accommodation (cycloplegia) and dilation of the pupil. (wikipedia.org)