Full sphere panoramas with semi-automatic stitching, using a tripod

John Strait
January 2006

This multi-step procedure can be used for multi-row, full 360 degree stitching.  Please be aware that this function was not specifically designed into The Panorama Factory V4. It is a pleasant surprise that it can be done at all and that it works so well.

Please note that this procedure requires V4.2 or newer.

This is a fairly lengthy process. It isn't too difficult if you have used a panoramic tripod head (e.g. Panosaurus) and have it properly set up (nodal point, etc).  If you do not own a panoramic tripod head, it is still a good idea to use your tripod to keep the camera orientation constant for all photos.  Multi-row stitching from handheld photographs is much more difficult and is outside the scope of this procedure.

This procedure assumes that the field of view is symmetric above and below the horizon and that the central row has a tilt angle equal to zero.  This means that the number of rows must be odd (3, 5, 7, etc.).

I have personally tested this procedure only for 3 row panoramas.  It may be possible to generalize it to 5 or more rows, but I have not tried this.

It may also be possible to generalize this procedure to an even number of rows, providing that the tilt angles are equal above and below the horizon.  However, again, I have not tried this.

Note that these instructions work only for full 360-degree multi-row stitching. Multi-row stitching of partial panoramas requires a somewhat different procedure.

For best results with this procedure I recommend:

  1. Use a good panoramic tripod head such as the Panosaurus from Gregwired Digital Images.  If you do not own a panoramic tripod head, you should use an ordinary tripod to keep the camera orientation constant for all photos in each row.
  2. Set it up the panoramic tripod head as perfectly as possible. Nodal point accuracy is important.
  3. Shoot the first row with tilt angle equal to zero.
  4. Without moving the tripod (very important), shoot two more rows with positive and negative pitch angles.  If you move the tripod, even if only by bumping one of the legs, this procedure may fail, in which case you'll need to use the instructions for hand held panoramas.
  5. It's best, but not absolutely necessary, to shoot the pictures in the three rows at the same horizontal index positions.
  6. It's probably best to use your camera in manual exposure mode so that all photos have the same exposure settings.

For three rows, you need an equal number of photos in each row to get adequate coverage. For more rows (e.g. 5), you may be able to reduce the number of photos in the upper and lower rows, but I have not personally tried this procedure yet with more than 3 rows.


Step A -- Stitch the central row

In this step, you stitch the central row of images into a 360 degree panorama.  This central row is used as the starting point for the full sphere panorama.  It establishes the focal length and the horizontal axis of the panorama.

  1. Start a new project and immediately Cancel the Wizard.

  2. Use the Import images... command (File menu) to import the images for all rows into the project file and make sure they are arranged left to right in each row, one row after the other.

  3. Select the thumbnails in the central row (tilt angle zero) and choose the Stitch with the Wizard command (New image menu).

  4. Choose Semi-automatic photo stitching on Wizard 2/9.

  5. Select Automatically detect focal length and Correct barrel distortion on Wizard 3/9.

  6. I recommend not selecting any checkboxes on Wizard 4/9.

  7. Select 360 degree panorama and Spherical projection on Wizard 5/9.

  8. Place stitching points on Wizard 6/9 to stitch the first row of the panorama.  I recommend this procedure for placing stitching points:

  9. Advance to Wizard 7/9.  Examine the preview image to be sure the stitch is accurate.  If it is not accurate, return to Wizard 6/9 to adjust stitching points or add new stitching points to other image pairs.

  10. Advance to Wizard 8/9 and select Prepare for internet display and Maximum size.

  11. Advance to Wizard 9/9 to complete the stitch and click Done to exit the Wizard.

  12. At this point, you should see a stitched and cropped thumbnail in the upper pane and the cropped image in the lower pane.


Step B -- Stitch the upper row

In this step, you stitch the upper row of images into a 360 degree panorama that is parallel to the central row.  If all goes well, this upper row will match the spherical coordinate system of the central row.

  1. Choose the Show imported images command (View menu) to display the imported thumbnails in the lower pane.

  2. Select the thumbnails for the upper row and choose the Stitch with the Wizard command (New image menu).

  3. This time, remove the checkmark from Automatically detect focal length and then choose I am certain of the focal length on Wizard 3/9. This guarantees all rows are stitched with the same focal length setting (the first stitch sets the Wizard value to the detected focal length).

  4. Advance to Wizard 6/9 and place stitching points on one image pair as you did for the first row.  As before, I recommend this procedure for placing stitching points:

  5. Advance to Wizard 7/9.  Examine the preview image to be sure the stitch is accurate.  If it is not accurate, return to Wizard 6/9 to adjust stitching points or add new stitching points to other image pairs.

  6. Advance to Wizard 9/9 to complete the stitch and click Done to exit the Wizard.  At this point, you should have two stitched thumbnails and two cropped thumbnails in the upper pane and the second cropped image in the lower pane.


Step C -- Stitch the lower row

In this step, you stitch the lower row of images into a 360 degree panorama that is parallel to the central row.  If all goes well, this lower row will match the spherical coordinate system of the central and upper rows.

  1. Choose the Show imported images command (View menu) to display the imported thumbnails in the lower pane.

  2. Select the thumbnails for the upper row and choose the Stitch with the Wizard command (New image menu).

  3. Complete the stitch of the lower row as you did for the first two rows.  Now you should have three stitched thumbnails and three cropped thumbnails in the upper pane and the second cropped image in the lower pane.


Step D -- Re-crop each of the stitched images to slightly more than 360 degrees

The first three steps have put each row onto the same spherical coordinate system.  The central row is at the Equator and the upper and lower rows follow the Tropics of Cancer and Capricorn (or higher or lower depending on the pitch axis).

In this fourth step, we re-crop each of the three individual rows to slightly more than 360 degrees.  This provides a little extra image at each end to allow for the row-to-row alignment.  In this example, we re-crop each row to 380 degrees.

  1. Right-click the thumbnail for the first cropped image and choose the Show source command from the Thumbnail image context menu.

  2. Select Horizontally symmetric on the Crop image dialog box and set Horizontal field of view to 380.

  3. Click Approve.

  4. Repeat steps 1, 2 and 3 for each cropped image.


Step E -- Resize all three cropped images to the same width

Note that the three cropped images have slightly different widths.  This happens because the alignment is never absolutely perfect.  But in any case, the images should be pretty close in size.  If they are very different (more than one or two percent), it probably indicates that one or more of the stitches did not turn out well.  If this happens, you should use the Restart the Wizard command (Image menu) to re-work the incorrect stitches.  It's really important to have good stitches for the three individual rows before advancing to the subsequent steps.

In this fifth step, we resize each of the three cropped images to the same width.  This helps to guarantee that the row-to-row stitching will work properly.  For example, you could set the width to 3800 degrees.  This is a convenient value because it is 10x the width in degrees.  This will simplify a later computation, but any other value could be used, for example, the width of one of the cropped images.

Do not worry about the image heights--it's OK if they are different.

If you use too large a value in this step, you will run out of memory in later steps because the finished full sphere image will be too large.  Note that the x64 Edition of The Panorama Factory effectively eliminates the out of memory error.  Refer to The Panorama Factory 64-Bit Edition for more information.

  1. Select all three cropped thumbnails at once. Click the first cropped thumbnail to select it and then hold the CTRL key while you click each of the other cropped thumbnails. After these clicks, you should be able to see that the three cropped thumbnails are selected and the stitched thumbnails are not selected.

  2. Choose the Resize command (New image menu). Answer Yes if you are asked whether you want to apply the command to the group of thumbnail images.

  3. Enter 3800 for W under New image size and leave H blank.

  4. Click OK.  This adds three resized thumbnails to the upper pane.


Step F -- Rotate the three resized images 90 degrees clockwise

At this point each image has a horizontal angular resolution of exactly 10 pixels per degree because we resized each 380 degree image to 3800 pixels.

In this step, we rotate the three resized images 90 degrees to prepare them for row-to-row stitching.

  1. Select all three resized thumbnails as you did with the cropped thumbnails. Actually, if you have not clicked anything on The Panorama Factoryís window, the resized thumbnails are automatically selected by the resize command.

  2. Choose the Rotate command (New image menu).

  3. Under Image rotation, enter 90 degrees and select Clockwise.

  4. Select Fit rotated image.

  5. Click OK.  This adds three rotated thumbnails to the upper pane.


Step G -- Stitch the rotated rows together

In this step, we stitch the rows together.

  1. Note that the three rows are in the wrong order.  They need to be in order from lower row to central row to upper row for stitching.  To move a thumbnail, first single-click it so that only one thumbnail is selected.  Then click and drag the thumbnail to its new position.

  2. Select all three rotated thumbnails at once. Click the first rotated thumbnail to select it and then hold the CTRL key while you click each of the other rotated thumbnails. After these clicks, you should be able to see that the three rotated thumbnails are selected and all other thumbnails are not selected.

  3. Choose the Stitch with the Wizard command (New image menu).

  4. Choose Manual document stitching on Wizard 2/9.  This stitching method joins the images without warping.  It is unnecessary to do any additional warping because the rows have already been converted to the spherical coordinate system.  This stitching method also permits the images to be different sizes. They are all 3800 wide, but the image heights vary.

  5. Advance to Wizard 4/7.  Surprisingly, you need not place any stitching points here!  Simply click the Next button and confirm that you want to advance to the next Wizard step.  You'll be prompted with a message box asking whether you want to advance with incomplete stitching points.  Click Yes.

    It is OK to advance without placing any stitching points.  This forces The Panorama Factory to perform automatic alignment on the images and usually produces the best results.  Placing stitching points carries the risk that the images may be rotated slightly during the alignment.  This is usually the right thing when actually stitching document scans, because it corrects for rotations of the document when placed on the document scanner.  However, in this multi-row procedure, we want to avoid any new rotation after the initial row stitches.

  6. Advance to Wizard 5/7.  Examine the preview image to be sure the stitch is accurate. You may need to adjust the preview resolution.  The default setting for preview resolution assumes you are stitching a normal panorama and it sometimes makes a poor choice here.  But in any case, do not set the preview resolution too large or this step will be very slow!

    If the stitch is not accurate, you should return to Wizard 4/7 and add stitching points.  We recommend that you only add one stitching point pair to each image pair.  A single stitching point pair defines the image-to-image alignment without introducing image rotation.

  7. Advance to Wizard 7/7 to complete the stitch and click Done to exit the Wizard.  You should see a new stitched thumbnail and a cropped thumbnail in the upper pane.  The cropped image is shown in the lower pane.


Step H -- Rotate the fully stitched image 90 degrees counter-clockwise

At this point each image has a horizontal angular resolution of about 10 pixels per degree because we resized each 380 degree image to 3800 pixels.

In this step, we rotate the fully stitched image back to its correct orientation.

NOTE: It is probably best to make manual adjustments to the stitched row images and the fully stitched image before starting this step.  If you see ghosts (faint double images), you can often correct them using the Fine tune command (Image menu) and/or with manual fine tuning.  For more information, refer to the section Fine tuning the image alignment in Chapter 6 of the online help, "Correcting stitching problems".  Sometimes ghost images cannot be eliminated with fine tuning, for example if an object (e.g. person or car) moved between the times you made two photographs.  You can sometimes remove these ghosts by adjusting the boundaries of the blending region.  For more information, refer to the section Adjust blending region boundaries in Chapter 4 of the online help, "Using the Classic interface, step by step".

  1. Double-click thumbnail of the fully stitched image to make it the current image shown in the lower pane.

    NOTE: You'll also see a cropped thumbnail in the upper pane, but we don't want to use this image.  The Wizard always crops the stitched image, but sometimes the cropping can introduce a small amount of image rotation.  This is usually the right thing in normal stitching (and, in fact, for the initial row stitches) because it corrects for small rotations that are left over after stitching.  However, in this multi-row procedure, we want to avoid any new rotation after the initial row stitches.

    So we double-click the stitched thumbnail.  The stitched image will display in the lower pane, with outlines superimposed on the image to indicate the image overlap regions.

  2. Choose the Rotate command (New image menu).

  3. Under Image rotation, enter 90 degrees and select Counter clockwise.

  4. Select Fit rotated image.

  5. Click OK.  This adds the rotated thumbnail to the upper pane and shows it in the lower pane.


Step I -- Crop the rotated image to exactly 360 degrees

In this step, we crop the rotated image to exactly 360 degrees.  Each of the row images is 380 degrees and the final stitched image is approximately 380 degrees, but probably slightly larger.

  1. Choose the Crop command (New image menu).

  2. Select Horizontally symmetric and enter 3600 for W under Cropped image size. This will crop the image to exactly 360 degrees because the images have a horizontal angular resolution of 10 pixels per degree.

    NOTE: We're entering 3600 because we cropped to 380 degrees in Step D and resized to 3800 in Step E.  If you use different values in Steps D or E, you must calculate the crop width this way:

    crop width = StepE_W * 360 / StepD_HFOV

  3. Click Approve.


Step J -- Sharpen the image if desired

This is the time to sharpen the image if you wish.

  1. Choose the Sharpen command (New image menu).

  2. Set sharpening parameters as you wish, or keep the defaults.

  3. Click Approve.


Step K -- Assign panoramic properties to the finished image

This step completes the full sphere image by marking it as a 360 degree panorama.

  1. Choose the Panoramic properties command (Image menu).

  2. Select This is a panoramic image and enter 360 for the HFOV under Horizontal field of view (degrees). The Panorama Factory will automatically calculate the Vertical field of view (degrees) for you.

  3. Click OK.


Step L -- Export the finished image

Finally, export the image to the desire format.  I recommend exporting in PTViewer format. You can also use IVR, but itís hard to find the IVR viewer these days. You cannot use QTVR because it does not support spherical projection. QTVR has a cubic format for full sphere panoramas, but PF does not support cubic QTVRs yet.

  1. Choose the Save current image as... command (File menu).  Select PTViewer from the Save as type dropdown list.  Then click PTViewer settings... to control how PTViewer displays your panorama.

  2. I like to add top and bottom caps to the full sphere image.  I usually make the top cap white and use a small BMP file for the bottom cap.

  3. Now sit back and enjoy the result of your hard work!


Revised: January 31, 2006

© 1999-2006 Smoky City Design, LLC and John Strait