Lens correction model - Revision history

Bronger: Removed half sentence about the d parameter; it was misguiding; all parameters have influence on the result image size. Moreover, the "d" parameters does more then mere scaling. Setting it wrongly results in failed un-distortion.

2012-11-30T16:51:15Z

Removed half sentence about the d parameter; it was misguiding; all parameters have influence on the result image size. Moreover, the "d" parameters does more then mere scaling. Setting it wrongly results in failed un-distortion.

Erik Krause: /* Optimize for lens correction */ corrected link

2012-11-02T12:00:50Z

‎Optimize for lens correction: corrected link

Erik Krause: linked to image positioning

2012-01-13T22:10:38Z

linked to image positioning

Zarl: Reverted edits by Annapanna111 (Talk) to last version by Erik Krause

2011-07-05T12:18:11Z

Reverted edits by Annapanna111 (Talk) to last version by Erik Krause

Annapanna111: /* Tools to correct barrel and pincushion distortion */

2011-07-05T09:40:23Z

‎Tools to correct barrel and pincushion distortion

Annapanna111 at 09:39, 5 July 2011

2011-07-05T09:39:14Z

Erik Krause: more links to correct dersch mirror

2011-06-10T07:30:01Z

Erik Krause: more links to correct dersch mirror

2010-09-25T09:30:36Z

Erik Krause: /* Field of View */ linked to working mirror

2010-09-25T09:24:09Z

‎Field of View: linked to working mirror

Bruno: /* Determine lens correction */ This should be a separate page really

2010-03-29T20:55:29Z

‎Determine lens correction: This should be a separate page really

@@ Line 37: / Line 37: @@
 Usual values for '''a''', '''b''' and '''c''' are below 1.0, in most cases below 0.01. Too high values suggest that you chose a wrong lens type, f.e. fisheye instead of rectilinear or vice versa. This refers to the absolute values of course since '''a''', '''b''' and '''c''' can be positive or negative (f.e. both 4.5 and -4.5 are considered too high values).
-The fourth parameter ('''d''') is only available in the [[Panorama Tools Plugins#Radial_Shift|Correct, Radial Shift]] filter of the [[Panorama Tools Plugins]]. It controls the result image size and is calculated implicitly by [[pano12]] (used by PTOptimizer, PTStitcher and the GUIs) in order to keep the same image size:
+The fourth parameter ('''d''') is only available in the [[Panorama Tools Plugins#Radial_Shift|Correct, Radial Shift]] filter of the [[Panorama Tools Plugins]]. It is calculated implicitly by [[pano12]] (used by PTOptimizer, PTStitcher and the GUIs) in order to keep the same image size:
 :<math>

@@ Line 96: / Line 96: @@
 The '''a''' and '''c''' parameters control more complex forms of distortion. In most cases it will be enough to optimize for the '''b''' parameter only, which is good at correcting normal [[barrel distortion]] and [[pincushion distortion]].
-If you want to see how changing the parameters influences distortion correction go to http://www.4pi.org/downloads/ and get '''abc.xls'''. Don't deactivate macros on loading.
+If you want to see how changing the parameters influences distortion correction go to http://4pi.org/downloads/ and get '''abc.xls'''. Don't deactivate macros on loading.
 See also [http://www.panotools.org/dersch/barrel/barrel.html Helmut Dersch's barrel distortion page].

← Older revision		Revision as of 22:10, 13 January 2012
Line 127:		Line 127:

	* [[Distortion Remove]] uses a completely different approach with a distortion matrix. Page in german only: http://www.stoske.de/digicam/Artikel/verzeichnung.html		* [[Distortion Remove]] uses a completely different approach with a distortion matrix. Page in german only: http://www.stoske.de/digicam/Artikel/verzeichnung.html
		+
		+	=== See also ===
		+	[[Image positioning model]]
		+

	[[Category:Glossary]]		[[Category:Glossary]]

@@ Line 126: / Line 126: @@
 * [[zhang_undistort]] is a tool distributed with [[hugin]] that uses [[CamChecker]] parameters to actually correct distortion.
-* [[Distortion Remove]] uses a completely different approach with a distortion matrix. Page in german only: http://www.stoske.de/digicam/Artikel/verzeichnung.html and info on swedish on lenses and glasses: http://www.glasogonpanatet.com/ , http://www.fargadelinser.eu
+* [[Distortion Remove]] uses a completely different approach with a distortion matrix. Page in german only: http://www.stoske.de/digicam/Artikel/verzeichnung.html
 [[Category:Glossary]]

@@ Line 126: / Line 126: @@
 * [[zhang_undistort]] is a tool distributed with [[hugin]] that uses [[CamChecker]] parameters to actually correct distortion.
-* [[Distortion Remove]] uses a completely different approach with a distortion matrix. Page in german only: http://www.stoske.de/digicam/Artikel/verzeichnung.html and info on swedish on lenses and glasses: http://www.glasogonpanatet.com/
+* [[Distortion Remove]] uses a completely different approach with a distortion matrix. Page in german only: http://www.stoske.de/digicam/Artikel/verzeichnung.html and info on swedish on lenses and glasses: http://www.glasogonpanatet.com/ , http://www.fargadelinser.eu
 [[Category:Glossary]]

@@ Line 15: / Line 15: @@
 The [[Focal Length]] is a physical property of the lens. Together with the effective sensor or film size and the focusing distance it approximates the image [[Field of View]] (there are other factors that influence it). '''Caution''': Cropping the image changes the Field of View. If you need to crop your source images for a panorama, crop them all to the same size!
-The Field of View together with the lens projection ([[Rectilinear Projection|rectilinear]], [[Fisheye Projection|fisheye]] or [[Cylindrical Projection|cylindrical]] for swing lens cameras) determine the image [[perspective distortion]]. Perspective distortion is less with a smaller Field of View. See Helmut Dersch page [http://www.all-in-one.ee/~dersch/perspective/Wide_Angle_Perspective.html] for details about different wide angle perspectives.
+The Field of View together with the lens projection ([[Rectilinear Projection|rectilinear]], [[Fisheye Projection|fisheye]] or [[Cylindrical Projection|cylindrical]] for swing lens cameras) determine the image [[perspective distortion]]. Perspective distortion is less with a smaller Field of View. See Helmut Dersch page [http://www.panotools.org/dersch/perspective/Wide_Angle_Perspective.html] for details about different wide angle perspectives.
 === Lens distortion a, b & c parameters ===
@@ Line 98: / Line 98: @@
 If you want to see how changing the parameters influences distortion correction go to http://www.4pi.org/downloads/ and get '''abc.xls'''. Don't deactivate macros on loading.
-See also [http://www.all-in-one.ee/~dersch/barrel/barrel.html Helmut Dersch's barrel distortion page].
+See also [http://www.panotools.org/dersch/barrel/barrel.html Helmut Dersch's barrel distortion page].
 There's an excellent tutorial on how to optimize by John Houghton: [http://johnhpanos.com/optitute.htm]

@@ Line 70: / Line 70: @@
 There are a number of ways to determine the a, b, c and [[Field of View|fov]]
-parameters for a particular lens/camera combination:
+parameters to calibrate a particular lens/camera combination:
-* Taking a single photograph of a subject containing straight lines, defining one or more sets of [[straight line control points]] (types t3, t4, etc.), and optimising for just a, b, c.  You need to set the output format to [[Rectilinear Projection]] for this technique to work.  This method is used by the author of [[PTLens]].
+* Taking a single photograph of a subject containing straight lines, defining one or more sets of [[straight line control points]] (types t3, t4, etc.), and optimising for just a, b, c.  You need to set the output format to [[Rectilinear Projection]] for this technique to work.  This method is used by the author of [[PTLens]].  The [[calibrate_lens]] tool also uses this technique and can operate with [[Fisheye Projection]] images greater than 180°.
-* Taking a single photograph of a rectangular object, selecting lots of [[horizontal control points|horizontal]] and [[vertical control points]], then optimising [[roll]], [[pitch]], [[yaw]], [[Field of View|fov]], a, b & c. You need to set the output format to [[Rectilinear Projection]] for this technique to work.  The process is similar to this [http://hugin.sourceforge.net/tutorials/architectural/ hugin architectural tutorial]:
+* Taking a single photograph of a rectangular or grid object, selecting lots of [[horizontal control points|horizontal]] and [[vertical control points]], then optimising [[roll]], [[pitch]], [[yaw]], [[Field of View|fov]], a, b & c. You need to set the output format to [[Rectilinear Projection]] for this technique to work.  The process is similar to this [http://hugin.sourceforge.net/tutorials/architectural/ hugin architectural tutorial]:
 * Taking two or more overlapping photographs and selecting lots of normal control points, then optimising [[roll]], [[pitch]], [[yaw]], [[Field of View|fov]], a, b & c. This technique works with any output [[Projections|projection format]] but requires [[parallax]] free images shot exactly from the [[Nodal Point]]. Note that to get a precise measure of the [[Field of View]], you have to take a full 360 degree panorama.
-* Using a tool such as [[PTLens]] or [[clens]] to read the [[JPEG]] [[EXIF]] data and correct the image automatically by looking up the lens in an existing database.
+* Using points that are known to be directly above each other such as edges of buildings, windows, reflections in ponds etc... This is the [[vertical control points]] method and works with [[Equirectangular Projection]] or [[Rectilinear Projection]] output and all lenses including those wider than 180°.
 === Optimize for lens correction ===