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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.

4 Responses

  1. The magenta image is hardly used because it is the last one integrated – By this time nearly all of the output area has image data already.

  2. Hi Yuval !

    First of all, thanks for your ideas, thanks to you I designed my own head http://cedricsimon.com/setup_2008_small.jpg

    I love the idea of rolling the camera, as I can now only take 4 shots with 450D + Sigma 8mm f3.5

    I would be happy if you could show us your conclusions with 4 shots instead of 6… Will it still take only the “good parts” of each photo ?

  3. @Bruno: I’ll have to dig back the pictures and try that again with changed order. If the reason really is the blending order, then for a 360° there will always be one picture that suffers and the seam placement algorithm of enblend has room for improvement.

    @Cédric: Nice setup! The rotator I use has only 60° increments and I use only three-shots for speed and six-shots for quality. I had it on a Manfrotto 300N for a little while, and I sometimes I have it on a pole. When on a pole, I take eight shots at 45°, but I don’t recall having done four around with a slanted head., sorry.

  4. Yes – when you are on a 1.6 crop like Canon there is nothing that gives you more than a 60° roll- like Luca Vascon says “ever 60°- never less then 4 images”.
    I slanted all the time and just made a session unslanted 5° up –> not bad at all really, but I will slant again because of the better zenith/nadir overlap. I do 4 shots all the times- quality speaking 6 – and I am very satified with the results.
    Ciao
    Mike

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