Banding artifacts

[Benjamin Schnieders]

Dear Hugin community,

after a two year absence, I returned to shooting panoramas. However, things have changed. I can't get Hugin/enblend to merge my pictures seamlessly. I attached two images, one being prior photometric optimization - sure, my lens has a bit vignetting, so vertical banding artifacts are to be expected. Then, after photometric optimization (tried it in different ways), at best a result like in the second image is achieved. I remember that Hugin / enblend used to deal with such minor brightness
deviations easily - I also tried several enblend options (including the much discussed --no-ciecam) but with not much changes.

Hugin version 2013.0.0.4692917e7a55 from official Ubuntu repos, enblend enblend 4.2-e4d6ae9dfe83 selfbuilt.

Any ideas what I'm doing wrong and what I could try? All my current panoramas seem to suffer from photometric optimization difficulties...


Thanks already,
Benjamin

[Terry Duell]

Hello Benjamin,

Same difficulties with all panos stitched with Hugin version
2013.0.0.4692917e7a55 and enblend 4.2-e4d6ae9dfe83, or have you had the
same problem with other versions/builds of enblend?

Is is possible to make a set of images and the .pto file available for one
of your smaller projects so we can see if the problem can be reproduced?
On Dropbox or similar.

Cheers,
--
Regards,
Terry Duell

[Benjamin Schnieders]

Hi Terry,

I had the same problems with the default-enblend from the Ubuntu repos. I built it myself to get a multithreaded/GPU accelerated version - but the problems persisted. (Plus the image cache version produced the good old horizontal black lines again.)

I uploaded a testcase to http://airesearch.de/files/static/testcase_hugin.zip - low quality jpeg files, shows the same artifacts as in the previous message with my setup. My wild guess would be that the photometric optimization doesn't work (as desired) for my images...

--
Regards,
Terry Duell

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[T. Modes]

Hi Benjamin,

Am Donnerstag, 18. September 2014 13:06:17 UTC+2 schrieb B. Schnieders:

Hi Terry,

I had the same problems with the default-enblend from the Ubuntu repos. I built it myself to get a multithreaded/GPU accelerated version - but the problems persisted. (Plus the image cache version produced the good old horizontal black lines again.)

I uploaded a testcase to http://airesearch.de/files/static/testcase_hugin.zip - low quality jpeg files, shows the same artifacts as in the previous message with my setup. My wild guess would be that the photometric optimization doesn't work (as desired) for my images...

The problem with your testsets are the black borders in your input images. I assume you have correct the lens distortion with another program, but the corrected images does not contain an alpha channel, which marks the pixels without information. So the images contains black borders which results in the effects you observed.
There are 3 possible ways to fix this:
1.) Add a crop to all images to crop the black borders in Hugin (on the masks tab)
2.) Check the settings of your program for lens correction. Export the images to a format with supports alpha channels (or transparency). JPG does not support alpha channels.
3.) Input the uncorrected images to Hugin. Hugin can also do the lens correction in the same run as remapping the images for the pano. This will yield to a better result, because the pixels needs only one time to interpolated (instead of twice as in your current workflow: one time for lens correction and one times for pano remapping).


Thomas

[Benjamin Schnieders]

Ohhhhh. Thanks Thomas. I don't know how I could miss that.

Yes, apparently ufraw performs a lens correction now and introduces black borders to each image by default. Thanks for your time, and good light :)

Benjamin


T. Modes wrote:
> Hi Benjamin,