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To Roll Or Not To Roll? – Part II

In this second part we look at how moving artefacts influence the seam placement. Here again, a different set of input images. The cars at the traffic light have moved between adjacent shots.

Before looking at how much each image contributes to the final panorama, let’s see where enblend puts the seams. This is possible with the option -l 1 which reduces the blending levels to 1. I am not aware of similar functions on the other blenders. Interestingly, seam placement in enblend is not very regular and the weight of the magenta picture, maybe affected by the moving artefacts, is strongly reduced.

And here is the resulting blend:

Obviously seam placement is influenced by the moving artefacts, though it seems not possible to predict it while shooting the scene. If it was, I could choose a convenient starting angle on the 360° around me isntead of starting at any random point, or at a specific cardinal point to use for orientating the panorama in a geographical context. Also for this specific case, like for many cases with moving objects, seam placement by enblend is not satisfying and will require further manual masking.

PTgui 8beta5 does a better job at seam placement, the panorama could be used as-is, although where there is such an overlap there are always two options and it is often a subjective artist decision which of the two to show. In this specific case, I could have wanted to show the empty street, and preferred the image without the cars.

Last but not least, two smartblend tests, once with 1.2.5 and once the version integrated in Autopano Pro. Also this time the result is different. It deals well with the moving artifacts, but not with the stitching error at the zenith.

As already shown previously by Michel Thoby, the blending process is unpredictable, and so it does not make sense to tweak camera orientation or starting angle in function of a potentially better blend. The slanted camera positioning does not introduce any disadvantage, and it retains its advantages. Conclusion: I’ll keep rolling my camera. YMMV.

Interact with the finished panorama here. It was my entry to this summer edition of the World Wide Panorama.

To Roll Or Not To Roll? – Part I

Above is how the footprint of the 8mm Sigma Fisheye relates to different sensor sizes. Below is my home-brew no-parallax-point (NPP) adapter. It aligns the rotation axis of the rotator with the NPP of the camera.

Ever since I started using an APS-C sensor dSLR camera with an 8mm fisheye lens to create full spherical panoramas, I’ve used a slanted pano head.

There are several advantages to a slanted pano head compared to a traditional one. The key advantage for me was a bigger overlap which allowed me to either produce a sphere with three shots only; or to quickly take six shots around and easily mask out moving objects at the seams.

Moreover, the edges of fisheye lenses are softer than the center, and such a setup should use more of the center and less of the edge. Or does it? A discussion triggered my curiosity.

I needed a method to visualize the contribution of each shot to the final panorama, without influencing the seam placement. Bruno Postle suggested to desaturate the images and colorize them. This method does not change the artefacts which determine seam placement. I used it once on a still scene with constant artefacts and once on a moving scene. In this article I present the results for the still scene.

Below are the six input pictures that were fed to the different contenders for warping and blending:

Enblend did quite regular slices out of the images, taking mostly the central part of them, where the lens quality is at its best.

PTgui 8beta5 has an interesting and more complex / less predictable blending pattern. It seems that all images available contributed to the zenith, and that even around the horizon the boundaries are not at regular intervals. More in depth analysis would be required to understand the pattern.

Smartblend 1.2.5 in PTgui yielded a result similar to Enblend, again slicing the images more or less regularly.

Interestingly, Smartblend inside Autopano Pro display a slightly different placement of the seams while still keeping them regularly distributed.

For still scenes, unless the blender used is the newest PTgui one, the logic seems to hold true that only the central, sharpest part of the image is used.

And here is the finished full spherical panorama, interactive and in its original color.