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Topic: Barrel distortion

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	Distortion
		Distortion is difficult to correct for in zoom lenses, which usually go from barrel at the wide end to pincushion at the tele end.
		Distortion is measured as the relative change of h compared to its value predicted by the paraxial theory.
		Distortion curve for the Distagon 2.8/21 (A, Zeiss data) and its derivative (B).
	www.vanwalree.com /optics/distortion.html (1625 words)

	Taming Barrel and Tilt Distortion
		The spherical distortion and its inverse can be readily implemented and applied in J. A script with these barrel distortion functions and a cover form is available from [6].
		radius to barrel distorted radius R_to_RD=: ] + [ * ^&3@] NB.
		While the software at [3] is faster than the functions described here, we have developed simple and effective tools for removing barrel distortion in J. One of the advantages of the J tools is that the source script is available, ready for modifications and improvements.
	www.vector.org.uk /archive/v201/cliff201.htm (1486 words)

	Nikon MicroscopyU: Interactive Java Tutorials - Geometric Distortion Aberrations
		Distortion is an aberration commonly seen in stereoscopic microscopy, and is manifested by changes in the shape of an image rather than the sharpness or color spectrum.
		Distortion is produced mainly by the oculars (between 5 and 10 percent of the radial distance) in optical microscopy, although some distortion is also found in lower quality objectives.
		Barrel distortion corresponds to a situation where the transverse magnification decreases with axial distance and each image point moves radially towards the center of the image.
	www.microscopyu.com /tutorials/java/aberrations/distortion (961 words)

	Barrel (disambiguation) - Wikipedia, the free encyclopedia
		Barrels for storage; especially Barrels for aging alcoholic beverages.
		Barrel as one of several units of volume measure (fluid for crude oil or beer, and dry for goods like fruits and vegetables).
		In Harry Turtledove's Timeline-191 alternate history series, 'barrel' refers to a tank.
	en.wikipedia.org /wiki/Barrel_(disambiguation) (137 words)

	wa (Site not responding. Last check: 2007-10-04)
		When the barrel distortion is corrected, the vignetting is removed but the effective field-of-view is reduced, making it about the same as the.75X Tiffen lens for wide-angle coverage.
		Barrel distortion correction is needed with this lens.
		Correction for barrel distortion is easier since vignetting is absent and, as a result, you see a bit larger field-of-view compared to the.75X Tiffen.
	members.aol.com /pixbydg/waweb/wa.html (836 words)

	L6-41.HTML (Site not responding. Last check: 2007-10-04)
		To obtain barrel distortion the lens must be about 12 cm from the wire mesh and the convex side of the lens must be facing the screen (set at left).
		To obtain pincushion distortion the lens must be about 18 cm from the wire mesh and the convex side of the lens must be facing the light source (set at left center).
		To obtain barrel distortion the lens must be about 18 cm from the wire mesh and the convex side of the lens must be facing the light source (set at right center).
	www.physics.umd.edu /lecdem/services/demos/demosl6/l6-41.htm (406 words)

	Barrel distortion
		Basically the barrel distortion is where horizontal and vertical lines bend outwards toward the edge.
		The distortion can be assuaged with the intelligent use of optical elements, electronic devices or software to counter-distort the picture in the image.
		By definition barrel distortion is allied with wide angle or minimal zoom lenses and as a result it causes the images to appear spherical or somewhat curved outward.
	www.snapjunky.com /digicam-advanced/barrel-distortion.shtml (1162 words)

	Imatest - Using Distortion
		Distortion tends to be most serious in extreme wide angle, telephoto, and zoom lenses.
		Distortion is normally centered around the geometric center of the image, but it may be decentered due to poor lens manufacturing quality or shock (i.e., dropping the lens).
		In this case, some residual barrel distortion is visible in vertical grid lines on the left and right and some residual pincushion distortion is visible in the horizontal grid lines on the top and bottom.
	www.imatest.com /docs/distortion.html (2912 words)

	Barrel and Pincushion Distortion Correction (Site not responding. Last check: 2007-10-04)
		Barrel distortion is associated with wide angle (or minimal zoom) lenses and it causes the images to appear spherical (curved outward).
		As opposite the Pincushion distortion is associated with Telephoto lenses (or maximum zoom) and the images appear pinched (bent inward) toward the center.
		For Barrel distortion most digital cameras should be in the range of 10 to 20 promille (or 1 to 2%).
	www.mediachance.com /pbrush/help/barrel.html (590 words)

	L6-40.HTML (Site not responding. Last check: 2007-10-04)
		To produce barrel distortion, position the wire mesh close to the first lens and position the large lens about 23 cm from the mesh to focus the image of the mesh on the screen, as shown in the photograph at the left below.
		The resulting barrel distortion is seen in the left center photograph.
		To produce pincushion distortion, position the wire mesh about 15 cm from the first lens and position the large lens about 23 cm from the mesh to focus the image of the mesh on the screen, as shown in the right center photograph below.
	www.physics.umd.edu /deptinfo/facilities/lecdem/services/demos/demosl6/l6-40.htm (306 words)

	Barrel Distortion: Optical: Glossary: Learn: Digital Photography Review
		Barrel distortion is a lens effect which causes images to be spherised or "inflated".
		Barrel distortion is associated with wide angle lenses and typically occurs at the wide end of a zoom lens.
		We measure barrel distortion in our reviews as the amount a reference line is bent as a percentage of picture height.
	www.dpreview.com /learn/?/Glossary/Optical/Barrel_Distortion_01.htm (152 words)

	creativepro.com - Photoshop How-To: Eliminate Barrel Distortion Caused by Camera Lenses
		Barrel distorion -- the slight convex curve that appears on straight lines in images -- is the necessary artifact of a camera's zoom lens.
		Because barrel distortion makes the outer areas of your image rounded, it's most apparent when there's a straight edge in the image, near the frame.
		First, we'll explain more in depth what barrel distortion is. Next, we'll go over one of the easiest methods you can use to eliminate it, focusing on the Free Transform tool and the Pinch filter.
	www.creativepro.com /story/feature/17837.html (1308 words)

	BreezeBrowser Pro - Lens distortion correction
		Lens distortion correction should not be applied to images that have been cropped because this will result incorrect adjustments resulting in distorted images.
		Barrel distortion is where the edges of the image bow outwards making the image barrel shaped.
		Pin cushion distortion is where the edges of the image bow inwards and is less common than barrel distortion.
	www.breezesys.com /BreezeBrowser/lens_distortion_correction.htm (506 words)

	Adjusting focal length and barrel correction
		The barrel correction and the focal length setting interact. It is easiest to adjust the barrel correction before setting the focal length value. This section describes a method for determining the correct barrel correction value.
		The same focal length value and barrel correction value apply to all images in your panorama. After adjusting the value, you should check the other overlap regions to be sure the value works well for your entire panorama.
		The barrel distortion is evident. What should be straight lines are seen as curves, bowing outward from the center of the image. Without correcting for this barrel distortion, the images cannot be properly matched. The following image shows the best that The Panorama Factory can do without applying a correction for the barrel distortion.
	www.panoramafactory.com /help/tip_focallength.html (830 words)

	[No title] (Site not responding. Last check: 2007-10-04)
		Barrel distortion on wide-angle lenses, and pincushion distortion on telephoto lenses, can be corrected in Panorama Tools.
		Lenses may exhibit pincushion distortion, barrel distortion, or a combination of both.
		Since distortion varies with target distance, photographs used for calibration should be taken at an appropriate distance.
	epaperpress.com /pano/calDistort.html (589 words)

	Lens distortion
		Most photographers will be aware of the barrel and pincushion distortion that typically appear at the shorter and longer ends of a zoom lens respectively, with continuous variation in between.
		Distortion affects different parts of the color spectrum differently (prism effect) and creates the so called "lateral chromatic aberration", which results in color fringes arround high/low-light transitions.
		However, when the distortion is more complex, varies with focus, and depends on the color plane, as is the case with a growing number of modern lenses, DxO is the only solution that can handle it.
	www.dxo.com /intl/photo/dxo_optics_pro/overview/optics_geometry_corrections/distortion (490 words)

	Creating a Gallery of Transformed Images (Image Processing Toolbox Image Transformation Demos) (Site not responding. Last check: 2007-10-04)
		Barrel distortion perturbs an image radially outward from its center.
		Pin-cushion distortion is the inverse of barrel distortion because the cubic term has a negative amplitude.
		Distortion is still greater farther from the center but it results in concave sides.
	www.clemson.edu /cle4_share/CWE/COES0915_CLUG/REFERENCE/matlabr14/toolbox/images/imdemos/html/tform.html (896 words)

	Digital camera pincushion distortion facts
		This discussion is important as it reveals the various importance of the topic of digital camera pincushion distortion and it's implications upon the entire performance of the digital camera as a device.
		Pincushion distortion is associated with tele lenses and typically occurs at the tele end of a zoom lens.
		As opposite the pincushion distortion is associated with telephoto lenses or maximum zoom and the images appear pinched or bent inward toward the center.
	www.snapjunky.com /digicam-advanced/digital-camera-pincushion-distortion-facts.shtml (1132 words)

	Correcting Barrel Distortion
		The most common and annoying lens error is barrel distortion, which occurs in many cheap wide angle lenses, especially in digital cameras or when using wide angle adapters.
		This counteracts barrel distortion, and is the basis for the above corrections.
		Finally, you may correct pincussion and barrel distortions in the same image: If the outer regions exhibit barrel distortions, and the inner parts pincussion, you should use negative 'a' and positive 'b' values.
	www.all-in-one.ee /~dersch/barrel/barrel.html (967 words)

	[No title]
		The most common and annoying lens error is barrel distortion, which occurs in many cheap wide angle lenses, especially in digital cameras or when using wide angle adapters.
		This counteracts barrel distortion, and is the basis for the above corrections.
		Finally, you may correct pincussion and barrel distortions in the same image: If the outer regions exhibit barrel distortions, and the inner parts pincussion, you should use negative 'a' and positive 'b' values.
	www.path.unimelb.edu.au /~dersch/barrel/barrel.html (960 words)

	Correcting Lens Distortion
		At 18 mm the 18 - 70 mm not only has barrel distortion, it has complex barrel distortion which is difficult to correct.
		As you can see even this nonlinear sort of barrel distortion is very well corrected.
		Barrel distortion is what has made the top of the hotel look curved.
	www.kenrockwell.com /tech/correctinglensdistortion.htm (400 words)

	Curvilinear Distortion in W.A. Large Format Lenses
		I am not just being a perfectionist, but this barrel distortion even in their normal 80mm lens truly detracts for me from the "believability and aesthetics" of the image.
		I have not noticed significant distortion in my 55mm Rodenstock APO Grandagon, though admittedly it is a recent purchase and I have not yet shot extensively with it yet.
		I am pretty sensitive to the barrel distortion that I have seen with 35mm wide-angle zoom lenses, but my guess is that barrel and pin-cushion distortion are rarely visible on modern large-format lenses.
	www.largeformatphotography.info /lfforum/topic/504526.html (1189 words)

	Correcting Optical Distortion by Thom Hogan
		At the wide angle focal length, most Coolpix models exhibit barrel distortion, while pin cushion distortion is sometimes found at the telephoto end.
		For barrel distortion, choose the Spherize filter from the Distort submenu on the Filter menu and enter a negative value (usually no more than –25; typically in the -5 to -10 range for Coolpix lenses).
		Third party programs exist that provide more automated and sophisticated distortion correction abilities: the two most often mentioned are a free tool written by Helmut Dersch, and while Andromeda Software has a Photoshop filter called LensDoc that is also quite helpful.
	www.bythom.com /distortion.htm (618 words)

	Digital Wide Zooms: Distortion
		They usually have some complex barrel distortion at their wide ends, are flat in the middle of the range and have just a hint of pincushion at their long ends.
		Distortion is insignificant except at 12 - 14 mm.
		There is more distortion in the Nikon 18 - 70 mm at 18 mm than in any of these.
	www.kenrockwell.com /tech/digital-wide-zooms/comparison-distortion.htm (920 words)

	PCWorld.com - Digital Focus: Wide-Angle Tips and Tricks
		One way to avoid barrel distortion is to simply avoid taking your wide-angle lens all the way to the limit.
		These programs may ask you to vary the lens distortion by some seemingly arbitrary value (a little experimentation and judicious use of the Undo button works wonders) or to simply identify the lines in the photograph, like a wall or horizon, that should be straight.
		Barrel distortion really bugs me. If I know that a line in a photograph--like the wall of a skyscraper or the horizon--is supposed to be straight, even a slight bow ruins the entire shot for me. That's why I adore LensDoc from Andromeda Software.
	www.pcworld.com /howto/article/0,aid,80884,00.asp (1581 words)

	Imatest - Distortion
		Distortion also calculates decentering: the deviation of the center of distortion symmetry from the geometric center of the image.
		Distortion can also be used with a single line if its curvature is visible.
		Distortion also produces a plot of intersection points (points where lines cross).
	www.imatest.com /docs/tour_distortion.html (505 words)

	BetterPhoto.com Q&A: What is Barrel Distortion?
		Strangely, 20 year old Minolta 50-mm f1.7s costing 1/6 as much have tested as having NO distortion, as well as exemplary resolution and contrast characteristics.
		On a related note, "pincushion" distortion is the opposite, straight lines at the edges of the frame bending inwards, like) (.
		If you're referring to the mention of barrel distortion in the 50 f/1.4 from this source - http://www.photo.net/equipment/canon/ef50/ then it should be noted that (a) the "test" was not scientific.
	www.betterphoto.com /forms/qnaDetail.asp?threadID=6586 (450 words)

	Landscape Photography and Nature Photography by Jim M. Goldstein - JMG-Galleries
		“Barrel Distortion, in which image magnification decreases with increasing distance from the optical axis.
		“Barrel distortion is a lens effect which causes images to be spherised or “inflated”.
		Barrel distortion is associated with wide angle lenses and typically occurs at the wide end of a zoom lens.
	www.jmg-galleries.com /blog (1860 words)

	Minimizing barrel distortion
		Barrel distortion occurs when taking photos at the widest angle of a lens.
		While not all barrel distortion looks bad and may even be desirable at times, you can minimize its effect by moving back and zooming in instead of standing close and shooting at wide angle.
		Watch the LCD for distortion as you zoom or change your physical distance from the set-up.
	www.digicamhelp.com /taking-photos/advanced-techniques/barrel-distortion.php (234 words)

	What is pincushion distortion? - A Word Definition From the Webopedia Computer Dictionary (Site not responding. Last check: 2007-10-04)
		A common type of distortion in CRT monitors in which horizontal and vertical lines bend inwards toward the center of the display.
		The distortion is most noticeable at the edges of the display.
		The opposite of pincushion distortion is barrel distortion, in which horizontal and vertical lines bend outwards toward the edge of the display.
	www.webopedia.com /TERM/P/pincushion_distortion.html (120 words)

	Super Wide-angle and distortion
		These results were acquired by taking a picture of a target at the selected focal lengths and guessing the distortion levels until the target lines became straight (free of barrel distortion).
		Set 'a' and 'c' to zero for all colors, choose a value for 'b' and choose 'd' so that d + b = 1.
		For barrel distortion compensation 'b' must be negative.
	www.fredmiranda.com /distortion (523 words)

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