Insta360 X6 DNG stitching workflow in PTGui 13.9

[360WW]

Has anyone successfully stitched a single Insta360 X6 DNG file in PTGui Pro 13.9?

So far I have not been able to get a correct result. The X6 DNG contains the two circular fisheye images side by side. I tried setting the lens type to Circular Fisheye, using the known workflow with the source image loaded twice, separate crop circles for the left and right fisheye, etc., but PTGui still does not produce a correct equirectangular panorama.

PTGui 13.9 appears to support the X3/X4/X5, but I have not found a working X6 workflow yet.

Does anyone have a reliable step-by-step workflow or PTGui template for the Insta360 X6 DNG files?

[John Houghton]

You should be able to get a stitch by following the instructions in the PTGui FAQ at https://www.ptgui.com/faq .  See sections 6.39 and 6.41.  However, you will not have enough overlap between the images for correct lens distortion parameters to be evaluated accurately, so the result is not going to be as good as it should be.  So, please take two shots, panning the camera around through 90 degrees or so between them. (Do this in a large venue or outdoors where things are generally far way).  What you do then is perform a stitch of the 4 fisheye images overlapping by 50%.  This enables lots of control points to be generated, well spread out.

Finally, you can then delete the pair of images from one shot and save the project for use as a template to stitch future shots.

Please make the pair of images (4 fisheye image circles) available for download somewhere (e.g. Dropbox, wetransfer.com  or other service) and post a link here.

John

[360WW]

Thank you! I’ll give it a try.

Will the next version of PTGui support the X6, and if so, when might it be available? 

[Philip Chong]

As soon as you can upload the DNG samples as per the instruction by John above for us to test, they will post a good template here, then another software update will include it.

That's  the pattern from what I see for new camera.

[360WW]

I only had a short opportunity to test this indoors, which is not ideal for calibration because the relatively short distances increase parallax. I also prefer not to upload photos of private rooms.

My basic procedure in PTGui Pro 13.9 was:

• Load each X6 DNG twice, because one DNG contains both fisheye images side by side.
• Use one copy for the left fisheye and the other for the right fisheye with individual crop settings.
• For calibration, take a second DNG after rotating the camera by about 90°, so PTGui has four fisheye images with much larger overlaps.
• Generate control points, then remove weak points on reflections, overexposed areas, soft edges and unclear details.
• First optimize FOV/focal length and image yaw/pitch/roll.
• Then also optimize lens distortion parameters a/b/c.
• Do not optimize lens shift, shear or fisheye factor.

The best indoor result so far was approximately:

• average control point distance: 10.87 px
• maximum: 22.30 px
• horizontal FOV: 199.17°
• a = -0.28
• b = +0.28
• c = +0.0071

The panorama looked quite good overall, but there is still a visible stitching error in the narrow overlap area between the two lenses. 
So I consider this a working test calibration, not a final X6 profile yet.

I am happy to share the PTGui template file for anyone who would like to test it with their own X6 DNGs.
Alternatively, if someone can provide a few X6 DNG files, ideally from outdoor scenes with distant structures, I would be happy to continue testing and refine the calibration.

[Scottio “Mr. MaGoogle” Wilson]

I can only assume new Insta360/X6 can be edited in the Insta360 Studio app. The last time I used it the app was free to download from their website. My workflow is to import the images to the proprietary software and export a panoramic image (Photo) to my local storage. That is when I continue forward to PTGUI to output a final presentation.

[360WW]

Thanks for the hint — that is indeed an important point. ;-) Insta360 Studio can stitch the X6 RAW files and export the finished equirectangular panorama as DNG as well.

Ideally, I would still like to handle the whole workflow in one application. I have been working with DSLR panoramas and PTGui for years, so PTGui is still my preferred tool, especially because of features such as manual masking and seam control, Nadir/stativ removal or replacement with a separate Nadir shot, correction of difficult stitching/parallax errors, and the more flexible handling of HDR/bracketed exposures.

For the X6, a combination of both may turn out to be the most practical solution: Insta360 Studio for the initial X6 RAW stitching, and PTGui when more control or correction is needed.

[John Houghton]

In theory at least, you should be able to add the Insta360 Studio panorama image to your PTGui project and create control points to align your camera images to that 360 image.  It might be worth trying . . . .

John

[360WW]

  My understanding would be:

1. Stitch the original X6 DNG in Insta360 Studio and export the finished panorama again as a DNG.
2. Load the original X6 dual-fisheye DNG twice in PTGui:
   • one copy cropped to the left fisheye
   • one copy cropped to the right fisheye
3. Add the Insta360 Studio stitched DNG as a third image and treat it as a 360° × 180° equirectangular panorama.
4. Keep the Studio panorama fixed as the reference image.
5. Create control points between the two original fisheye images and the corresponding areas in the Studio panorama.
6. Let PTGui optimize the X6 fisheye geometry against that reference, mainly:
   • relative yaw/pitch/roll of the two lenses
   • horizontal FOV / focal length
   • lens distortion parameters a/b/c
   • possibly lens shift if necessary
7. Then remove the Studio reference image and save the resulting two-image X6 setup as a reusable PTGui template.

The idea would be to use Insta360 Studio’s own X6 lens/stitching model as a reference for building a better PTGui calibration, especially for the narrow overlap area where my current manual calibration still shows a stitching error.

Is that roughly what you had in mind, and would you consider this a valid way to derive a PTGui template from the Studio-stitched panorama?

[John Houghton]

Yes, that is what I had in mind.  Just one point:  in item 6, lens shift should indeed be optimised using individual shift parameters, since there are two separate lenses having different offsets of their optical centres.

John