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Topic: Aperture stop

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	Aperture - Wikipedia, the free encyclopedia
		For a telescope, for example, the aperture stop is typically the edges of the objective lens or mirror (or of the mount that holds it).
		The pupil of the eye is its aperture; the iris is the diaphragm that serves as the aperture stop.
		Reducing the aperture size increases the depth of field, which describes the extent to which subject matter lying closer than or farther from the actual plane of focus appears to be in focus.
	en.wikipedia.org /wiki/Aperture (1749 words)

	F-number - Wikipedia, the free encyclopedia
		In a camera, this is typically the diaphragm aperture, which can be adjusted to vary the size of the pupil, and hence the amount of light that reaches the film or image sensor.
		The aperture stop is the aperture 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.
		It may simply be the opening of the aperture stop, or may be a magnified image of the aperture stop, formed by elements within the lens.
	en.wikipedia.org /wiki/F-number (2629 words)

	Stops and Apertures
		This aperture is the aperture stop for the shown position of the object.
		The aperture stop determines the solid angle of the transmitted light cone for an on-axis object.
		The image of the aperture stop seen through all the optical elements to the left of the aperture stop is the aperture stop itself, since there are no optical elements to the left of it.
	electron9.phys.utk.edu /optics421/modules/m3/Stops.htm (1771 words)

	Aberration in optical systems - Wikipedia, the free encyclopedia
		This hole is termed the stop or diaphragm; Abbe used the term aperture stop for both the hole and the limiting margin of the lens.
		It requires the middle of the aperture stop to be reproduced in the centres of the entrance and exit pupils without spherical aberration.
		In telescopes aperture is usually taken as the linear diameter of the objective.It is not the same as microscope aperture which is based on the entrance pupil or field of view as seen from the object and is expressed as an angular measurement.
	en.wikipedia.org /wiki/Aberration_in_optical_systems (6088 words)

	Stops and Pupils (Site not responding. Last check: 2007-10-18)
		The correct use of stops and pupils is vital to minimizing the background radiation reaching the detector on a telescope.
		If the aperture stop of a telescope is the primary mirror, the exit pupil is the image of the primary formed by the secondary.
		Because the center of the aperture stop and the exit pupil are on the axis of the telescope, the chief ray appears to come from the center of the exit pupil.
	astron.berkeley.edu /~jrg/Telescopes/node5.html (527 words)

	Digital Camera Aperture \| Camera Aperture
		The Aperture stop of any camera lens is usually expressed in 'f' numbers -- the higher the 'f' number the smaller the aperture.
		Aperture stop and shutter speed are directly related to each other in determining the amount of light that enters a camera.
		Since a large aperture can be used in conjunction with a fast shutter speed, this is often a good combination for action shots because the fast shutter speed will 'freeze' the movement with a minimum of blurring.
	www.alkenmrs.com /digital-photography/digital-cameras-aperture.html (653 words)

	New Page 1
		Note that eyepiece vignetting occurs on the side of the eyepiece field stop which is opposite that of the vignetting from an aperture stop.
		Without any internal aperture stops the entrance pupil of the binocular is the objective lens itself and the exit pupil is defined to be the image of the entrance pupil formed by the eyepiece.
		However if the internal aperture stop does protrude below the sloping line as in the lower of the figure below, then the new exit pupil is reduced in size and appears further to the right shown as the short red line next to the old exit pupil.
	www.kwic.com /~amj/bino.html (2414 words)

	Spectrohelioscope
		The lens L and the aperture stop A are separated by twice the focal length F of the lens.
		The entrance pupil coincides with the aperture stop since there are no lenses or mirrors to the left of A. This is not the case for the exit pupil which is located at the image A' of the aperture stop.
		The aperture stop is at the grating G. Since G is placed in the focal plane of the mirror C, C and O form an image of the aperture stop located 1800 mm in front of O. This is the location of the entrance pupil.
	home.hetnet.nl /~c.severijns/Spectrohelioscope_bestanden/Optics.htm (3073 words)

	A Tedious Explanation of the f/stop
		The ratio is between the diameter of the aperture in the lens and the focal length of the lens.
		If they say they got some ASA 400 film which is two stops faster than their Sensia II, it means it is four times as sensitive and you can infer that the Sensia was ASA 100 (from 400, 200 would be one stop, one halving, and 100 would be the second stop, the second halving).
		There is a concept called t/stop, for transmission stop, which is a measure of the actual light transmission of the lens rather than the simple ratio of the aperture to the focal length.
	www.uscoles.com /fstop.htm (3423 words)

	What Is... Aperture? - Digital Photography Tutorial - Photoxels
		The aperture of a lens is the diameter of the lens opening and is usually controlled by an iris.The larger the diameter of the aperture, the more light reaches the film / image sensor.
		In practice, unless you are dealing with a fixed-aperture lens (many simple point-and-shoot cameras have only one fixed aperture), the aperture of a lens is usually expressed as a range of fstops.
		aperture for the wide-angle (F2.8) and telephoto (F3.5) focal lengths of a zoom lens.
	www.photoxels.com /tutorial_aperture.html (1749 words)

	F-Stop and Aperture, Still Photography Camera Guide stsite.com
		This figure is derived from dividing the focal length of the lens by the aperture opening of the lens.
		The aperture is the opening formed by a system of metal leaves in the lens that open up and close down to control the volume of light passing through the lens.
		Now you have learnt that the larger the aperture the more light can pass through thus enabling you to take pictures indoor or in poor lighting condition, so if you use your camera indoor most of the time you should look for cameras with an aperture of at least f2.
	www.stsite.com /camera/cam04.php (796 words)

	Canon Digital Photography Forums - What's a stop?
		As for f-stop vs. stop, 1 f-stop refers directly to 1 aperture stop while stop simply refers to half (or double, as the case may be) the amount of light.
		Stops (which get's the name from a historical gadget) are either a doubling or halving of the amount of light.
		The reason these weird aperture numbers are used is because they tell a whole lot about depth of field,depth of focus,hyperfocus,etc and are completely interchangeable from one lens to another.
	photography-on-the.net /forum/printthread.php?t=36772&pp=50 (1908 words)

	ABERRATION - LoveToKnow Article on ABERRATION (Site not responding. Last check: 2007-10-18)
		The component Si of the system, situated between the aperture stop and the object O, projects an image of the diaphragm, termed by Abbe the "entrance pupil": the "exit pupil " is the image formed by the component S2, which is placed behind the aperture stop.
		the system is made infinitely narrow by reducing the aperture stop; such a pencil consists of the rays which can pass from the object point through the now infinitely small entrance pupil.
		For a single lens of very small thickness and given power, the aberration depends upon the ratio of the radii r:r', and is a minimum (but never zero) for a certain value of this ratio; it varies inversely with the refractive index (the power of the lens remaining constant).
	www.1911ency.org /A/AB/ABERRATION.htm (7070 words)

	Articles - Aberration in optical systems (Site not responding. Last check: 2007-10-18)
		This hole is termed the ´´stop´´ or ´´diaphragm´´;; Abbe used the term ´´aperture stop´´ for both the hole and the limiting margin of the lens.
		The component S1 of the system, situated between the aperture stop and the object O, projects an image of the diaphragm, termed by Abbe the ´´entrance pupil´´;; the ´´exit pupil´´; is the image formed by the component S2, which is placed behind the aperture stop.
		The preceding review of the several errors of reproduction belongs to the ´´Abbe theory of aberrations,´´; in which definite aberrations are discussed separately; it is well suited to practical needs, for in the construction of an optical instrument certain errors are sought to be eliminated, the selection of which is justified by experience.
	www.newmirror.com /articles/Aberration_in_optical_systems (5278 words)

	ABCD - Online Information article about ABCD
		All rays which issue from 0 and pass through the aperture stop also pass through the entrance and exit pupils, since these are images of the aperture stop.
		The,the with an angle of aperture smaller than u* would not have the same distance of intersection and the same sine ratio; these deviations are called "zones," and the constructor endeavours to reduce these to a minimum.
		The same holds for the errors depending upon the angle of the field of view, w: astigmatism, curvature of field and distortion are eliminated for a definite value, w*; " zones of astigmatism, curvature of field and distortion " attend smaller values of w.
	encyclopedia.jrank.org /A10_ADA/ABCD.html (7443 words)

	Canon Digital Photography Forums - f-stop different from aperture? ?
		the aperture value of 6.0 indicates a fraction of an f-stop so I suspect the software is telling you that the aperture was set at 6.0, but the equivilant f-stop was 8.0.
		The square root of 2 raised to the 6th (aperture) is 8 (f-stop), and the square root of 2 raised to the 5.5th is f/6.7.
		However, because this is a variable max aperture lens, setting the same physical aperture size results in an effective exposure of f6 when shot wide (max f3.5) and f8 when shot narrow (max f4.5).
	photography-on-the.net /forum/printthread.php?t=14873&pp=40 (1070 words)

	Aperture in photography
		One of the trend is - the aperture value is now control via a thumb wheel on the camera (usually near the shutter release button) and the AF lens has no aperture ring to alter the value.
		Basically, aperture, along with duration/timing of the shutter curtain opening, BOTH contribute to a the formation of an exposure.
		For example: use larger aperture (Smaller number like f/2.8, f/2.0 etc.) with a long focal length to isolate or emphasis on expression, such as in portraiture photography; or use a smaller aperture (Bigger number like f/16 or f/22 etc..) to ensure pin-sharp details in both the foreground and the background.
	www.mir.com.my /rb/photography/fototech/apershutter/aperture.htm (1713 words)

	[No title]
		A stop 8 mm in diameter is placed halfway between an extended object and a large- diameter lens of 9 cm focal length.
		If a stop 15 mm in diameter is placed halfway between the lenses and serves as an aperture stop: Where is the entrance pupil?
		An aperture of opening 5 cm in diameter positioned 15 cm to the left of a positive lens of rim diameter 10 cm and focal length 12 cm.
	www.nova.edu /~bjiang/lectures_files/GO_problems_Ch_10.doc (435 words)

	New Page 1
		An internal aperture stop is anything that restricts the light cone from the objective reaching the eyepiece.
		Note that eyepiece vignetting occurs on the right side of the eyepiece field stop which is opposite that of the vignetting from an aperture stop.
		But the profile of the internal aperture stop is circular so the portion of light from the objective that is wasted will include the purple region on the right side of the vertical line as well.
	www.kwic.com /~amj/binoinside.html (1240 words)

	Nikon's meter indexing mechanisms
		The relative stop down is determined by "counting" the number of stops between the proposed taking aperture (set by the photographer) and the maximum aperture of the lens.
		The twist to the minimum aperture side releases the mechanism and the following twist to the maximum aperture side slides the body's pin, which is linked to an internal resistor band, to a position which is determined by the maximum aperture.
		Electrical aperture indexing is in a way a draw back from direct relative indexing to maximum aperture indexing but it has the advantage that a variable maximum aperture can be precisely indexed.
	www.zi.ku.dk /personal/lhhansen/photo/indexing.htm (1294 words)

	SportsShooter.com - ERR message/aperture stop-down problem
		Checked to make sure the aperture was stopping down correctly and it wasn't.
		I removed the lens and the aperture acutation lever wasn't moving.
		Below is one of the shots after the aperture started working again.
	www.sportsshooter.com /message_display.html?tid=9590 (327 words)

	F-Stop
		f-stop (or f-number) is a measurement of the size of the aperture (opening) of the camera iris.
		If the aperture is wider, more light enters the lens and the picture is brighter.
		Note that a small f-stop (large aperture) results in a small depth of field and a larger f-stop (smaller aperture) gives a large depth of field.
	www.mediacollege.com /glossary/f/f-stop.html (158 words)

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