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03-26-2019, 12:02 PM   #16
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QuoteOriginally posted by emalvick Quote
The question with regard to using auto perspective is how is the software doing it. Is it taking into account metadata and lens so that an image with a specific lens is adjusted the same way?
In the case of DT the answer is no. DT analyzes near-horizontal and near-vertical straight lines in the image and tries to adjust them to absolute vertical and/or horizontal, regardless of the lens used.

03-26-2019, 12:56 PM   #17
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QuoteOriginally posted by kaseki Quote
I guess that would require at least some spatial adjustment as any two pairs of points on two images might not have exactly the same spacing.
The basic process is Hugin is that it uses the lens data (angle of view and projection, such as rectilinear vs. fish-eye ...), and a distortion model for the lens, to calculate an imaginary projection of your images to a sphere - a big ball around the rotation point of your camera on which your image resides (also visualized in the UI). It identifies common points in the source images and then arranges your pictures on that sphere in a way that the identical points match best. As part of that, it can optimize its distortion model for your lens, so that the points most closely overlap. Now it applies a chosen projection (cyclindrical, Mercator, ...) of that arranged spherical image onto your canvas for the final output. This is where you can adjust how you want to view the result, including perspective correction. The resulting combined mathematical transformation of your source image to its contribution on your canvas is then applied in a single remapping step and the different pictures finally blended into each other.

The above omits a number of other adjustments (exposures, HDR stacks), but I hope it helps to understand the Hugin UI.
03-26-2019, 03:36 PM   #18
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QuoteOriginally posted by newmikey Quote
In the case of DT the answer is no. DT analyzes near-horizontal and near-vertical straight lines in the image and tries to adjust them to absolute vertical and/or horizontal, regardless of the lens used.
I would think this could then cause a problem. Hugin tries to take advantage of the specific optics to make adjustments so that you can get a good stiching. If you count on software to automatically do the adjustment, and it is just basing it on interpreted geometry, Hugin will only be able to guess on how to make the adjustment.

This may not be a big deal when you are dealing with panoramas coming from less extreme focal lengths, but if you start getting at very wide angle or fisheye shots, then you could have issues.

Now, Hugin is pretty good, and it may be able to overcome the issue anyway, but I generally eliminate any middle processing as much as possible with regard to lens corrections because I want to let the software that is built for stitching do what it needs to do.
03-26-2019, 04:32 PM   #19
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From my test, auto perspective adjustment in darktable worked well with DA15mm.
Hugin stitched super wide panorama did not benefit from that tool.

03-26-2019, 09:36 PM   #20
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QuoteOriginally posted by emalvick Quote
I would think this could then cause a problem. Hugin tries to take advantage of the specific optics to make adjustments so that you can get a good stiching. If you count on software to automatically do the adjustment, and it is just basing it on interpreted geometry, Hugin will only be able to guess on how to make the adjustment.

This may not be a big deal when you are dealing with panoramas coming from less extreme focal lengths, but if you start getting at very wide angle or fisheye shots, then you could have issues.

Now, Hugin is pretty good, and it may be able to overcome the issue anyway, but I generally eliminate any middle processing as much as possible with regard to lens corrections because I want to let the software that is built for stitching do what it needs to do.
You are absolutely correct on all points. I would not use DT and Hugin this way but the TS wanted to know whether it is possible. It is.
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