• size
• The iris is a thin, circular structure in the eye, responsible for controlling the diameter and size of the pupils and thus the amount of light reaching the retina. (absoluteastronomy.com)
• It is meant as a method for correcting photometric measurements of luminance values impinging on the human eye by scaling them by the effective pupil size. (wikipedia.org)
• In photography, the size of the entrance pupil (rather than the size of the physical aperture itself) is used to calibrate the opening and closing of the diaphragm aperture. (wikipedia.org)
• The accommodation reflex (or accommodation-convergence reflex) is a reflex action of the eye, in response to focusing on a near object, then looking at distant object (and vice versa), comprising coordinated changes in vergence, lens shape and pupil size (accommodation). (wikipedia.org)
• To use an optical instrument, the entrance pupil of the viewer's eye must be aligned with and be of similar size to the instrument's exit pupil. (wikipedia.org)
• 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)
• astronomical
• The 9 x 63mm SkyMaster DX has a wide 5° field and very bright 7mm exit pupils ideal for serious low power/wide field astronomical viewing. (astronomics.com)
• infinity
• Dramatic enhancement in contrast levels observed with epi-fluorescence illuminators in infinity-corrected systems is attributed to the optical advantage of longer tube lens focal lengths. (microscopyu.com)
• luminance
• The troland typically refers to the ordinary or photopic troland, which is defined in terms of the photopic luminance: T = L × p {\displaystyle \mathrm {T} =\mathrm {L} \times \mathrm {p} } , where L is the photopic luminance in cd m−2 and p is pupil area in mm2. (wikipedia.org)
• A scotopic troland is also sometimes defined: T ′ = L ′ × p {\displaystyle \mathrm {T'} =\mathrm {L'} \times \mathrm {p} } , where L′ is the scotopic luminance in cd m−2 and p is pupil area in mm2. (wikipedia.org)
• Troland does not directly convert to other units, being a retinal luminance per unit area of a pupil. (wikipedia.org)
• Assuming the corneal luminance L from an extended source, the pupil diameter p and the focal length of the eye F, the retinal luminance is: Lr [lm / m^= pi * L / 4 / (f/#)^2 ~ pi * L * p^2 / 4 / F^2. (wikipedia.org)
• Tripod
• A panoramic tripod head is a piece of photographic equipment, mounted to a tripod, which allows photographers to shoot a sequence of images around the entrance pupil of a lens that can be used to produce a panorama. (wikipedia.org)
• produce
• Tube lengths between 200 and 250 millimeters are considered optimal, because longer focal lengths will produce a smaller off-axis angle for diagonal light rays, reducing system artifacts. (microscopyu.com)
• object
• The 200 mm lens's entrance pupil has four times the area of the 100 mm lens's entrance pupil, and thus collects four times as much light from each object in the lens's field of view. (wikipedia.org)
• He says, "At this point it will be sufficient to note that all these formulae involve quantities relating exclusively to the entrance-pupil and its position with respect to the object-point, whereas the focal length of the transforming system does not enter into them. (wikipedia.org)
• system
• Longer tube lengths also increase the flexibility of the system with regard to the design of accessory components. (microscopyu.com)
• In addition, moving this slider to longer tube lengths decreases the angle θ between on-axis and off-axis light rays passing through the system. (microscopyu.com)
• smaller
• the eyes adduct, the ciliary muscles contract, and the pupils become smaller. (wikipedia.org)
• photography
• According to the Focal Encyclopedia of Photography (1965), "A bibliography of his 571 books and articles was published in Forschungen zur Geschichte der Optik, 1943. (wikipedia.org)
• increase
• During accommodation, the pupil constricts to increase the depth of focus of the eye by blocking the light scattered by the periphery of the cornea. (wikipedia.org)
• area
• Multiplying by the pupil area : Trolands [cd / m^2 * mm^= L * pi * p^2 / 4 = F^2 * Lr ~ 289 * Lr. (wikipedia.org)
• sometimes
• Older literature on optics sometimes refers to the exit pupil as the Ramsden disc, named after English instrument-maker Jesse Ramsden. (wikipedia.org)