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Topic: Chromatic aberration

	Chromatic aberration - Wikipedia, the free encyclopedia
		Chromatic aberration is caused by the dispersion of the lens material, the variation of its refractive index n with the wavelength of light.
		Chromatic aberration of a lens is seen as "fringes" of color around the image, because each color in the optical spectrum cannot be focused at a single common point on the optical axis.
		Chromatic aberration can be further minimized by using an achromatic doublet or achromat in which two materials with differing dispersion are bonded together to form a single lens.
	en.wikipedia.org /wiki/Chromatic_aberration (281 words)

	Lens (optics) - Wikipedia, the free encyclopedia
		Spherical aberration is caused because spherical surfaces are not the ideal shape with which to make a lens, but they are by far the simplest shape to which glass can be ground and polished and so are often used.
		Spherical aberration can be minimised by careful choice of the curvature of the surfaces for a particular application: for instance, a plano-convex lens which is used to focus a collimated beam produces a sharper focal spot when used with the convex side towards the beam.
		Chromatic aberration of a lens is seen as fringes of color around the image.
	en.wikipedia.org /wiki/Lens_(optics) (1970 words)

	Chromatic aberrations
		The chromatic aberration is particularly manifest in wideangle lenses of the retrofocus type and with older-generation tele lenses.
		Lateral color is referred to as a chromatic variation of distortion, while LCA combines with spherical aberration to a phenomenon known as spherochromatism [12,13].
		Spherical aberration and LCA are independent of the position of the aperture stop, but their adverse effect on the image quality is reduced upon stopping down the lens.
	www.vanwalree.com /optics/chromatic.html (2263 words)

	Chromatic Aberration
		The amount of chromatic aberration depends on the dispersion of the glass.
		Another approach to chromatic aberration reduction is to use two positive lenses separated by one half the sum of their wavelengths.
		Chromatic aberration for three colors can be eliminated with and apochromat triplet.
	hyperphysics.phy-astr.gsu.edu /hbase/geoopt/aber2.html (297 words)

	Canon BCTV Lenses: What is Chromatic Aberration?
		Chromatic aberration arises from dispersion- the property that the refractive index of glass differs with wavelength.
		In fig focal length is plotted on the horizontal axis and on-axis chromatic aberration on the vertical axis.
		In Fig focal length is plotted on the horizontal axis and lateral chromatic aberration on the vertical axis.
	www.canon.com /bctv/faq/chrab.html (351 words)

	HDTV lens design: Management of chromatic aberrations
		Chromatic aberrations are the nemesis of the HDTV lens —; especially in its small 2/3in image format embodiment.
		The primary chromatic aberration, where the chromatic lens is focused for the central green portion of the spectrum, and the opposite ends of the visible spectrum defocus differentially.
		While the chromatic aberration may indeed be present, it is generally invisible to the human eye even on a large HDTV screen.
	broadcastengineering.com /mag/broadcasting_hdtv_lens_design_3 (2163 words)

	aberration on Encyclopedia.com (Site not responding. Last check: 2007-11-07)
		Spherical aberration is caused by the failure of a lens or mirror of spherical section to bring parallel rays of light to a single focus.
		Chromatic aberration results in the blurred coloring of the edge of an image when white light is sent through a lens.
		Electron microscopes stand corrected: correction for the spherical aberration of lenses in electron microscopes is allowing scientists to push the resolution into the sub-angstrom range, opening the doors to new...
	www.encyclopedia.com /html/a1/aberrati.asp (728 words)

	Aberration
		Chromatic aberrations are caused by dispersion (the variation in the index of refraction of a medium with wavelength).
		Monochromatic aberrations are caused by geometry (the shape of the lens or mirror).
		Spherical aberration occurs because the focal length of a lens varies with distance from the principal axis.
	hypertextbook.com /physics/waves/aberration/index.shtml (328 words)

	Chromatic aberration (Site not responding. Last check: 2007-11-07)
		We have seen that both mirrors and lenses suffer from spherical aberration, an effect which limits the clarity and sharpness of the images formed by such devices.
		For many years chromatic abberation was a sufficiently serious problem for lenses that many scientists tried to find ways of reducing the number of lenses in scientific instruments, or even eliminating them all together.
		The two lenses in an achromatic doublet are made of different type of glass with indices of refraction chosen such that the combination brings any two chosen colours to the same sharp focus.
	farside.ph.utexas.edu /teaching/302l/lectures/node126.html (236 words)

	Eliminating color fringing (lateral chromatic aberration)
		Longitudinal chromatic aberration is the change of the lens's point of focus for different wavelengths.
		Lateral chromatic aberration is the change in a lens's magnification for different wavelengths, resulting in color fringing.
		It tends to be worst in highly asymmetric lenses, particularly in retrofocus ultrawides (<24mm in the 35mm format), where the rear element may be further from the film than the focal length, and in true telephotos (>200mm in the 35mm format), which may be shorter than the focal length.
	www.normankoren.com /Tutorials/Chromatic.html (1034 words)

	Chromatic Aberration in Introductory Labs
		Chromatic aberration in lenses is an important concept in practice, but one that is not frequently studied in introductory courses, particularly in introductory labs.
		The goal of this work is to show that the ‘chromatic aberration’ can in fact be measured as part of such as exercise, primarily using the equipment that would normally be used for this exercise.
		One might also be able to enhance the aberration by using other schemes for finding the focus, such as the autocollimation method, in which the light passes twice through the lens, which should enhance the aberration.
	www.neiu.edu /~pjdolan/aberr.html (974 words)

	OLYMPUS MIC-D: Interactive Java Tutorial - Chromatic Aberration (Site not responding. Last check: 2007-11-07)
		Chromatic aberrations are wavelength-dependent artifacts that occur because the refractive index of every optical glass formulation varies with wavelength.
		Chromatic aberration (see Figure 1) artifacts are compounded by the difference in image magnification that occurs as a result of the varying focal planes for each color group, an effect termed chromatic difference of magnification.
		Aberration of this type can be significantly reduced, or eliminated, by making compound lenses that are composed of individual elements having different color-dispersing properties.
	www.mic-d.com /java/chromatic (613 words)

	rft's photography / Tips & Tricks / Correcting Chromatic Aberration of Digital Cameras (Site not responding. Last check: 2007-11-07)
		Chromatic aberration is a deficiency of the lens that results in colour fringes that are only present on the peripheral parts of a photo.
		Another clear indication of chromatic aberration is, that the coloured fringes only appear on non-radial edges and their colour depends on the orientation with respect to the center.
		Obviously a correction of chromatic aberration after the colour interpolation has been performed in the camera can never be as good as a possible correction before colour interpolation has taken place.
	ray.cg.tuwien.ac.at /rft/Photography/TipsAndTricks/Aberration (1757 words)

	Lens Power and Chromatic Aberration (Site not responding. Last check: 2007-11-07)
		Since we are beginning the study of aberration, one thing we will need to know is what shape a lens, or, for that matter, a mirror, of a given focal length will have.
		A lens with one flat surface, and one curved surface of radius r has a focal length of r/(N-1), where N is the index of refraction of the material the lens is made of (divided by the refractive index of the surrounding medium).
		Another is to determine how to abolish both kinds of chromatic aberration at once by using two lenses in close contact made from two different kinds of glass, so that their total power is the same, at least for two wavelengths of light.
	www.hypermaths.org /quadibloc/science/opt0504.htm (1829 words)

	Melles Griot Optics Guide - Chromatic Aberration
		Spherical aberration, distortion, coma, and field curvature are purely a function of the shape of the lens surfaces and an be observed with monochromatic light.
		Longitudinal chromatic aberration is defined as the axial distance from the nearest to the farthest focal point.
		As in the case of spherical aberration, positive and negative elements have opposite signs of chromatic aberration.
	www.mellesgriot.com /products/optics/fo_3_2_6.htm (212 words)

	EF-S 17-85mm f/4-5.6 IS USM Chromatic Aberration
		The Canon EF-S 17-85mm f/4-5.6 IS USM lens with the EOS 20D shows mild chromatic aberration in the outer 39% of the image field that is comparable to the chromatic aberration produced by the highly rated EF 28-135mm f/3.5-5.6 IS USM with full frame sensors or film.
		Mild chromatic aberration was observed in the outer 39% area of the image field.
		Moderate chromatic aberration was observed in the outer 61% area of the image field at 55mm with the EF-S 18-55mm lens.
	www.wlcastleman.com /equip/reviews/20D/20Dlenses/ca.htm (157 words)

	PhotoNotes.org Dictionary - Chromatic aberration (Site not responding. Last check: 2007-11-07)
		Typically, special glass with a low refractive index (ED glass for Nikon and UD glass and fluorite for Canon) is used to correct for chromatic aberration, particularly on telephoto and retrofocus wide-angle lenses, both of which have very assymetrical lens designs.
		Technically there are two forms of chromatic aberration - longitudinal (or axial) and lateral (or transverse (TCA) or chromatic difference of magnification).
		Lateral chromatic aberration is very common on inexpensive lenses and cannot be reduced by reducing the lens aperture.
	photonotes.org /cgi-bin/entry.pl?id=Chromaticaberration (362 words)

	Compensating for chromatic aberration
		Chromatic Aberration is a common lens defect in which the lens focuses different frequencies (colors) of light differently.
		One type of chromatic aberration results in the different colors being in focus, but each color's image is a slightly different size.
		This type of aberration results in complementary color fringing in areas away from the center of the image.
	pdesigner.net /photoshopcs/1_5_5_9.html (280 words)

	Powershot Chromatic Aberrations
		Digital camera chromatic variations seem to be a fact of life.
		Each of the detail images are taken from opposite sides of the image, and you can see that the fringing on the Powershot tends to be on the side of a highlight that faces away from the lens center.
		Lateral aberration is related to the wavelength of the light, and so when aberration occurs, longer wavelengths (reds) will tend to be away from the center of the optical axis, while shorter wavelengths (blues) will tend to be toward the center.
	www.botzilla.com /photo/G1chroma.html (1280 words)

	RetouchPRO - Chromatic Aberration
		It's called chromatic aberration and it's caused because different wavelengths of light are refracted differently.
		In the case of camera lenses the aberration is typically spherical and therefore is most severe at the edges of the frame where the light is bent at the greatest angle.
		Do a search on Google with keywords 'scanner' 'chromatic' and 'aberration' and you will see quite a few articles on the subject.
	www.retouchpro.com /forums/printthread.php?t=1595 (196 words)

	Chromatic Aberration (Site not responding. Last check: 2007-11-07)
		Chromatic Aberrations are color deviations of lens systems.
		These aberrations are usually the result of defective optics, poor coatings on lenses, or viewing targets through telescopes when the line of sight is not co-axial to the cylinder of the telescope.
		The best way to detect Chromatic Aberrations in magnification systems is to look through the lens(es) at a fl and white image, preferably one with sharp lines of demarcation.
	www.dentistry.ubc.ca /research/ergonomics/chromab3.htm (207 words)

	Correcting Chromatic Aberrations
		Using software applications such as Adobe Photoshop, it is possible to decrease the visibility of the chromatic aberrations.
		Move the image on the screen so that the chromatic aberration is visible.
		Move the image around the screen to make sure all the chromatic aberration is eliminated from the whole image.
	www.outdooreyes.com /photo26.php3 (326 words)

	INSTRUMENTS - Online Information article about INSTRUMENTS (Site not responding. Last check: 2007-11-07)
		Cass their aberrations have a tendency to correct each other; grafts.
		The chromatic aberration of the object-glass of one of these telescopes is corrected for photographic rays, and the image formed by it is received on a highly sensitive photographic plate.
		The other telescope is corrected for visual rays and its image is formed on the plane of the spider-lines of a filar micrometer.
	encyclopedia.jrank.org /I27_INV/INSTRUMENTS.html (6915 words)

	Digital Light & Color Message Boards: Amazing chromatic aberration correction
		The images were very sharp, but the chromatic aberration was unbelievably terrible.
		I needed to both adjust the red magnification and move the center point of the aberration.
		Note that moving the center point of the aberration is very important
	www.dl-c.com /discus/messages/2/2491.html?1081895465 (114 words)

	Sony DSC-F828 Review: 16. Photographic tests: Digital Photography Review
		We'll call it 'purple fringing' but it's clearly a combination of chromatic aberrations caused by the interaction of the lens and the microlenses on the sensor and enhanced by a certain amount of blooming which carries the color out further than the original artifact.
		While worse at full wide angle and maximum aperture (28 mm equiv., F2.0) it is visible throughout the zoom range and at smaller apertures.
		Iniital results have certainly been mixed, with some excellent images exhibitting superb resolution to others with strong chromatic aberrations or visible noise.
	www.dpreview.com /reviews/sonydscf828/page16.asp (628 words)

	Canon Digital Photography Forums - Chromatic Aberration
		Your description of the aberration is exactly how it displays, primarily on the edges of the trees.
		More likely, flare would be marginally worse using the ND filter, since there would now be a couple of additional glass surfaces in the light path - namely, those of the ND filter, itself.
		Chromatic Aberrations are very common when using AWB on the G3.
	photography-on-the.net /forum/printthread.php?t=16077 (622 words)

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