How to Calibrate Camera Optics - Revision history

Andrew at 15:16, 13 August 2018

2018-08-13T15:16:20Z

Andrew at 15:13, 13 August 2018

2018-08-13T15:13:50Z

Andrew at 15:12, 13 August 2018

2018-08-13T15:12:14Z

Andrew at 15:09, 13 August 2018

2018-08-13T15:09:16Z

Andrew at 08:40, 2 August 2018

2018-08-02T08:40:01Z

Andrew: saving to file

2018-08-02T08:36:42Z

saving to file

Andrew: scales comparison

2018-08-02T08:10:52Z

scales comparison

Andrew at 07:27, 2 August 2018

2018-08-02T07:27:04Z

Andrew at 21:24, 1 August 2018

2018-08-01T21:24:47Z

Andrew: results

2018-08-01T20:20:55Z

results

@@ Line 26: / Line 26: @@
 * Click '''Show Pattern''' button in toolbar of '''PATTERN''' tab of '''Camera Optics Calibration''' tool:
 <center>[[File:camera-calibration-show-pattern-button.png|link=]]</center>
-* Start video recording and shoot this pattern from different view angles. For each view:
+* Start video recording and shoot this pattern from different view points. For each view:
 ** Ensure the pattern fills most of the frame. It's OK if the whole screen doesn't feet into the frame.
 ** Hold the camera still for a second.
@@ Line 79: / Line 79: @@
 <center>[[File:camera-calibration-open-video-button.png|link=]]</center>
 * Video will be automatically converted to internal [[.iPiVideo File Extension|.iPiVideo]] file format.
-* Using "Toggle Current Frame" button in toolbar choose frames with different view angles:
+* Using "Toggle Current Frame" button in toolbar choose frames with different view points:
 ** where the pattern fills most of the frame
 ** where camera is not moving significantly
-** one frame for each view angle type is enough
+** one frame for each view point type is enough
 * Application will show detected markers in selected frame. It's OK if some of markers weren't detected.
 ** If you don't like results of detection, you can deselect the frame by clicking '''Toggle Current Frame''' button again and try different frame(s) from video.
 <center>[[File:camera-calibration-frames-selection.png|800px]]</center>
-* As soon as you choose at least three frames (we recommend to use five frames corresponding to five view angles described above) you can run calculation of camera optics parameters by clicking on '''Run Calibration''' button in toolbar.
+* As soon as you choose at least three frames (we recommend to use five frames corresponding to five view point types described above) you can run calculation of camera optics parameters by clicking on '''Run Calibration''' button in toolbar.
 ** Also, you can change calibration options using controls located near this button. But in most cases default values work like a charm.
 * Now you're on '''RESULT''' tab and see calculated parameters of camera optics:
 <center>[[File:camera-calibration-results-tab.png|600px]]</center>
-{{Tip|You can play with sample calibration video: [http://files.ipisoft.com/samples4/four-gopro/internal-calib/cam1-720p-wide.MP4 cam1-720p-wide.MP4] (13 MB). We recommend to choose the following frames: <tt>50</tt> ("front" view angle), <tt>880</tt> ("from the left" view angle), <tt>1360</tt> ("from the right" view angle), <tt>1780</tt> ("from the top" view angle), <tt>2110</tt> ("from the bottom" view angle).}}
+{{Tip|You can play with sample calibration video: [http://files.ipisoft.com/samples4/four-gopro/internal-calib/cam1-720p-wide.MP4 cam1-720p-wide.MP4] (13 MB). We recommend to choose the following frames: <tt>50</tt> ("front" view point), <tt>880</tt> ("from the left" view point), <tt>1360</tt> ("from the right" view point), <tt>1780</tt> ("from the top" view point), <tt>2110</tt> ("from the bottom" view point).}}
 == Undistorting and Scale ==
@@ Line 137: / Line 137: @@
 * Save parameters of camera to <tt>.iPiCam</tt> file on disc by clicking on '''Save''' button in toolbar.
-** {{Tip|We recommend to name file using camera nickname/label, resolution and FOV setting. For example: <tt>cam1-720p-wide.iPiCam</tt>, where <tt>1</tt> is label on camera, <tt>720p</tt> — video resolution setting, <tt>wide</tt> — view angle setting. This would help to choose and apply right camera parameters to undistort video in '''Combined Video Builder''' tool.}}
+** {{Tip|We recommend to name file using camera nickname/label, resolution and FOV setting. For example: <tt>cam1-720p-wide.iPiCam</tt>, where <tt>1</tt> is label on camera, <tt>720p</tt> — video resolution setting, <tt>wide</tt> — view/FOV setting. This would help to choose and apply right camera parameters to undistort video in '''Combined Video Builder''' tool.}}
 * You'll use this file later — during creation of synchronized multi-camera video from individual MP4/AVI/MOV/MPEG video files from cameras. See [[How to Build Synced Multi-Camera Video]] for details.

@@ Line 29: / Line 29: @@
 ** Ensure the pattern fills most of the frame. It's OK if the whole screen doesn't feet into the frame.
 ** Hold the camera still for a second.
-* We recommend to use the following five view angles:
+* We recommend to use the following five view points:
 <center><table border=0>
-<tr><td>'''View Angle'''</td>
+<tr><td>'''View Point'''</td>
 <td align="center">'''How it Looks from Side'''</td>
 <td align="center">'''How it Looks from Top'''</td>

@@ Line 16: / Line 16: @@
 * Mark camera by some label to distinguish it from others.
 : For example:
-<center>[[File:action-cameras-labels-sample.jpg|400px|link=]]</center>
+<center>[[File:action-cameras-labels-sample.jpg|400px]]</center>
 * Set view-angle and resolution you're going to use during motion capture session(s).
 : {{Tip|720p (1280 x 720) resolution is recommended for full body motion capture needs in most cases (except very large capture area).}}

@@ Line 15: / Line 15: @@
 * Mark camera by some label to distinguish it from others.
 * Set view-angle and resolution you're going to use during motion capture session(s).
-* {{Tip|720p (1280 x 720) resolution is recommended for full body motion capture needs in most cases (except very large capture area).}}
+: {{Tip|720p (1280 x 720) resolution is recommended for full body motion capture needs in most cases (except very large capture area).}}
-* {{Important|If you use [https://shop.gopro.com/cameras GoPro] action camera, please don't use [https://gopro.com/help/articles/question_answer/What-is-SuperView SuperView] mode because in this mode calibration will fail (thanks to special "dynamic stretches" from 4:3 to 16:9 format made by camera software).}}
+: {{Important|If you use [https://shop.gopro.com/cameras GoPro] action camera, please don't use [https://gopro.com/help/articles/question_answer/What-is-SuperView SuperView] mode because in this mode calibration will fail (thanks to special "dynamic stretches" from 4:3 to 16:9 format made by camera software).}}
 * If your camera has zoom and/or auto-focus features then these features must be turned off before calibration because this procedure is valid only for fixed optics.
 * Run [[iPi Recorder]] and click '''Calibrate Camera Optics''' button in toolbar:

@@ Line 125: / Line 125: @@
 <td></td>
 <td align="center" valign="top">Almost all pixels from original image present on undistorted one (result/effective FOV is about the same as original FOV) but effective vertical resolution on undistorted image is too low (as a result we loose detailing for objects near the center).</td>
-<td align="center" valign="top">Looks as a reasonable balance between effective FOV and effective vertical resolution.</td>
+<td align="center" valign="top">Looks as a reasonable balance between loss in FOV and loss in vertical resolution.</td>
 <td align="center" valign="top">There is no green areas on undistorted image but we loose a lot of pixels from original image (result/effective FOV is too small in comparison with original one).</td>
 </tr>

@@ Line 91: / Line 91: @@
 {{Tip|You can play with sample calibration video: [http://files.ipisoft.com/samples4/four-gopro/internal-calib/cam1-720p-wide.MP4 cam1-720p-wide.MP4] (13 MB). We recommend to choose the following frames: <tt>50</tt> ("front" view angle), <tt>880</tt> ("from the left" view angle), <tt>1360</tt> ("from the right" view angle), <tt>1780</tt> ("from the top" view angle), <tt>2110</tt> ("from the bottom" view angle).}}
-== Result ==
+== Undistorting and Scale ==
 Camera parameters are used to remove distortion from video. This allows to process video in [[iPi Mocap Studio]] just like video from web-camera with good optics (without significant distortion and principal point shift).
@@ Line 129: / Line 129: @@
 </tr>
 </table></center>

@@ Line 106: / Line 106: @@
 By default scale is automatically selected to balance (1) and (2). But you can adjust it manually if needed. But be aware that low values of scale result in degradation of image quality on undistorted video (because pixel size of all objects on video becomes smaller). And high values of scale result in significant narrowing of field-of-view (FOV) after undistorting.
-<center><table border=0>
+<center><table border=0 width="1090">
 <tr>
-<td></td><td  rowspan="4">&nbsp;&nbsp;&nbsp;</td>
+<td width="100"></td><td rowspan="4" width="10"></td>
-<td align="center">Scale = 0.65</td><td rowspan="4">&nbsp;&nbsp;&nbsp;</td>
+<td align="center" width="320">Scale = 0.65</td><td rowspan="4" width="10"></td>
-<td align="center">Scale = 0.80</td><td rowspan="4">&nbsp;&nbsp;&nbsp;</td>
+<td align="center" width="320">Scale = 0.80</td><td rowspan="4" width="10"></td>
-<td align="center">Scale = 0.90</td>
+<td align="center" width="320">Scale = 0.90</td>
 </tr>
 <tr>
@@ Line 124: / Line 124: @@
 <tr>
 <td></td>
-<td align="center" valign="top">...</td>
+<td align="center" valign="top">Almost all pixels from original image present on undistorted one (result/effective FOV is about the same as original FOV) but effective vertical resolution on undistorted image is too low (as a result we loose detailing for objects near the center).</td>
-<td align="center" valign="top">...</td>
+<td align="center" valign="top">Looks as a reasonable balance between effective FOV and effective vertical resolution.</td>
-<td align="center" valign="top">...</td>
+<td align="center" valign="top">There is no green areas on undistorted image but we loose a lot of pixels from original image (result/effective FOV is too small in comparison with original one).</td>
 </tr>
 </table></center>

@@ Line 20: / Line 20: @@
 * If your camera has zoom and/or auto-focus features then these features must be turned off before calibration because this procedure is valid only for fixed optics.
 * Run [[iPi Recorder]] and click '''Calibrate Camera Optics''' button in toolbar:
-<center>[[Image:camera-calibration-tool-button.png|link=]]</center>
+<center>[[File:camera-calibration-tool-button.png|link=]]</center>
 * To calibrate camera optics special calibration pattern is used. You have to record this pattern shown on computer screen from different view points.
 * Click '''Show Pattern''' button in toolbar of '''PATTERN''' tab of '''Camera Optics Calibration''' tool:
-<center>[[Image:camera-calibration-show-pattern-button.png|link=]]</center>
+<center>[[File:camera-calibration-show-pattern-button.png|link=]]</center>
 * Start video recording and shoot this pattern from different view angles. For each view:
 ** Ensure the pattern fills most of the frame. It's OK if the whole screen doesn't feet into the frame.
@@ Line 37: / Line 37: @@
 <tr><td colspan=4><hr></td></tr>
 <tr><td>1. Front</td>
-<td align="right">[[Image:camera-calibration-front-view-side.png|x200px|link=]]</td>
+<td align="right">[[File:camera-calibration-front-view-side.png|x200px|link=]]</td>
-<td align="center" valign="top">[[Image:camera-calibration-front-view-top.png|300px|link=]]</td>
+<td align="center" valign="top">[[File:camera-calibration-front-view-top.png|300px|link=]]</td>
-<td align="center">[[Image:camera-calibration-front-view-proj.png|x150px|link=]]</td>
+<td align="center">[[File:camera-calibration-front-view-proj.png|x150px|link=]]</td>
 </tr>
 <tr><td colspan=4><hr></td></tr>
 <tr><td>2. From the left</td>
-<td align="right">[[Image:camera-calibration-left-view-side.png|x200px|link=]]</td>
+<td align="right">[[File:camera-calibration-left-view-side.png|x200px|link=]]</td>
-<td align="center" valign="top">[[Image:camera-calibration-left-view-top.png|300px|link=]]</td>
+<td align="center" valign="top">[[File:camera-calibration-left-view-top.png|300px|link=]]</td>
-<td align="center">[[Image:camera-calibration-left-view-proj.png|x200px|link=]]</td>
+<td align="center">[[File:camera-calibration-left-view-proj.png|x200px|link=]]</td>
 </tr>
 <tr><td colspan=4><hr></td></tr>
 <tr><td>3. From the right</td>
-<td align="right">[[Image:camera-calibration-right-view-side.png|x200px|link=]]</td>
+<td align="right">[[File:camera-calibration-right-view-side.png|x200px|link=]]</td>
-<td align="center" valign="top">[[Image:camera-calibration-right-view-top.png|300px|link=]]</td>
+<td align="center" valign="top">[[File:camera-calibration-right-view-top.png|300px|link=]]</td>
-<td align="center">[[Image:camera-calibration-right-view-proj.png|x200px|link=]]</td>
+<td align="center">[[File:camera-calibration-right-view-proj.png|x200px|link=]]</td>
 </tr>
 <tr><td colspan=4><hr></td></tr>
 <tr><td>4. From the top</td>
-<td align="right">[[Image:camera-calibration-top-view-side.png|x200px|link=]]</td>
+<td align="right">[[File:camera-calibration-top-view-side.png|x200px|link=]]</td>
-<td align="center" valign="top">[[Image:camera-calibration-top-view-top.png|300px|link=]]</td>
+<td align="center" valign="top">[[File:camera-calibration-top-view-top.png|300px|link=]]</td>
-<td align="center">[[Image:camera-calibration-top-view-proj.png|x150px|link=]]</td>
+<td align="center">[[File:camera-calibration-top-view-proj.png|x150px|link=]]</td>
 </tr>
 <tr><td colspan=4><hr></td></tr>
 <tr><td>5. From the bottom</td>
-<td align="right">[[Image:camera-calibration-bottom-view-side.png|x200px|link=]]</td>
+<td align="right">[[File:camera-calibration-bottom-view-side.png|x200px|link=]]</td>
-<td align="center" valign="top">[[Image:camera-calibration-bottom-view-top.png|300px|link=]]</td>
+<td align="center" valign="top">[[File:camera-calibration-bottom-view-top.png|300px|link=]]</td>
-<td align="center">[[Image:camera-calibration-bottom-view-proj.png|x150px|link=]]</td>
+<td align="center">[[File:camera-calibration-bottom-view-proj.png|x150px|link=]]</td>
 </tr>
 </table></center>
@@ Line 75: / Line 75: @@
 ** The best option here is to use SD-card reader. But USB cord also do the trick but slower.
 * Switch to '''CALIBRATION''' tab in '''Camera Optics Calibration''' tool in [[iPi Recorder]] and open this video by clicking '''Open Video''' button in toolbar:
-<center>[[Image:camera-calibration-open-video-button.png|link=]]</center>
+<center>[[File:camera-calibration-open-video-button.png|link=]]</center>
 * Video will be automatically converted to internal [[.iPiVideo File Extension|.iPiVideo]] file format.
 * Using "Toggle Current Frame" button in toolbar choose frames with different view angles:
@@ Line 83: / Line 83: @@
 * Application will show detected markers in selected frame. It's OK if some of markers weren't detected.
 ** If you don't like results of detection, you can deselect the frame by clicking '''Toggle Current Frame''' button again and try different frame(s) from video.
-<center>[[Image:camera-calibration-frames-selection.png|800px]]</center>
+<center>[[File:camera-calibration-frames-selection.png|800px]]</center>
 * As soon as you choose at least three frames (we recommend to use five frames corresponding to five view angles described above) you can run calculation of camera optics parameters by clicking on '''Run Calibration''' button in toolbar.
 ** Also, you can change calibration options using controls located near this button. But in most cases default values work like a charm.
 * Now you're on '''RESULT''' tab and see calculated parameters of camera optics:
-<center>[[Image:camera-calibration-results-tab.png|600px]]</center>
+<center>[[File:camera-calibration-results-tab.png|600px]]</center>
 {{Tip|You can play with sample calibration video: [http://files.ipisoft.com/samples4/four-gopro/internal-calib/cam1-720p-wide.MP4 cam1-720p-wide.MP4] (13 MB). We recommend to choose the following frames: <tt>50</tt> ("front" view angle), <tt>880</tt> ("from the left" view angle), <tt>1360</tt> ("from the right" view angle), <tt>1780</tt> ("from the top" view angle), <tt>2110</tt> ("from the bottom" view angle).}}
@@ Line 96: / Line 96: @@
 On the '''RESULT''' tab you can click on some frame in left panel and get preview of distortion removing ("undistorting"):
-<center>[[Image:camera-calibration-undistort-preview.jpg|link=]]</center>
+<center>[[File:camera-calibration-undistort-preview.jpg|link=]]</center>
 As you can see, there is a big difference in geometry of boundaries because of radial distortion. As a result, part of pixels from original (top) image are not visible in undistorted (bottom) image. And in turn, on undistorted (bottom) image there are areas filled by green color: the thing is that, corresponding pixels on source (i.e. original) image are beyond of boundaries.
@@ Line 108: / Line 108: @@
 <center><table border=0>
 <tr>
-<td align="center">Scale = 0.65</td><td>&nbsp;&nbsp;&nbsp;</td>
+<td></td><td  rowspan="4">&nbsp;&nbsp;&nbsp;</td>
-<td align="center">Scale = 0.80</td><td>&nbsp;&nbsp;&nbsp;</td>
+<td align="center">Scale = 0.65</td><td rowspan="4">&nbsp;&nbsp;&nbsp;</td>
 <td align="center">Scale = 0.90</td>
 </tr>
 <tr>
-<td>[[Image:camera-calibration-scale-0.65.jpg|317px|link=]]</td><td></td>
+<td align="right">Original<br/>image</td>
-<td>[[Image:camera-calibration-scale-0.80.jpg|317px|link=]]</td><td></td>
+<td rowspan="2">[[File:camera-calibration-scale-0.65.jpg|317px|link=]]</td>
-<td>[[Image:camera-calibration-scale-0.90.jpg|317px|link=]]</td>
+<td rowspan="2">[[File:camera-calibration-scale-0.80.jpg|317px|link=]]</td>
 </tr>
 </table></center>

← Older revision		Revision as of 21:24, 1 August 2018
Line 105:		Line 105:

	By default scale is automatically selected to balance (1) and (2). But you can adjust it manually if needed. But be aware that low values of scale result in degradation of image quality on undistorted video (because pixel size of all objects on video becomes smaller). And high values of scale result in significant narrowing of field-of-view (FOV) after undistorting.		By default scale is automatically selected to balance (1) and (2). But you can adjust it manually if needed. But be aware that low values of scale result in degradation of image quality on undistorted video (because pixel size of all objects on video becomes smaller). And high values of scale result in significant narrowing of field-of-view (FOV) after undistorting.
		+
		+	<center><table border=0>
		+	<tr>
		+	<td align="center">Scale = 0.65</td><td>   </td>
		+	<td align="center">Scale = 0.80</td><td>   </td>
		+	<td align="center">Scale = 0.90</td>
		+	</tr>
		+	<tr>
		+	<td>[[Image:camera-calibration-scale-0.65.jpg\|317px\|link=]]</td><td></td>
		+	<td>[[Image:camera-calibration-scale-0.80.jpg\|317px\|link=]]</td><td></td>
		+	<td>[[Image:camera-calibration-scale-0.90.jpg\|317px\|link=]]</td>
		+	</tr>
		+	</table></center>

← Older revision		Revision as of 20:20, 1 August 2018
Line 92:		Line 92:

	== Result ==		== Result ==
		+
		+	Camera parameters are used to remove distortion from video. This allows to process video in [[iPi Mocap Studio]] just like video from web-camera with good optics (without significant distortion and principal point shift).
		+
		+	On the '''RESULT''' tab you can click on some frame in left panel and get preview of distortion removing ("undistorting"):
		+	<center>[[Image:camera-calibration-undistort-preview.jpg\|link=]]</center>
		+
		+	As you can see, there is a big difference in geometry of boundaries because of radial distortion. As a result, part of pixels from original (top) image are not visible in undistorted (bottom) image. And in turn, on undistorted (bottom) image there are areas filled by green color: the thing is that, corresponding pixels on source (i.e. original) image are beyond of boundaries.
		+
		+	Using '''Scale''' parameter you can adjust proportion between two quantities:
		+	# how many pixels on original image are beyond boundaries of undistorted image (pixels which lay down out of green-line boundaries on the top image)
		+	# how many pixels on undistorted image have no corresponding (source) ones on original image (green pixels on the bottom image)
		+
		+	By default scale is automatically selected to balance (1) and (2). But you can adjust it manually if needed. But be aware that low values of scale result in degradation of image quality on undistorted video (because pixel size of all objects on video becomes smaller). And high values of scale result in significant narrowing of field-of-view (FOV) after undistorting.