automatically solving vignetting at sunrise and down in a series of panoramas

[Maarten Verberne]

Hi,
i create panoramas with 2 images where the sun comes up on one side and
goes down in the other corner.

however, at sun down and rise i have vignetting in the opposite corner,
eg, it's darker there...you might say this is expected behaviour and i
would agree.

when the sun is really low this creates a V shaped form, a while later
this becomes a dark band and eventually is fades and is gone.

while this is all expected the trouble starts when i stitch those frames
together with a command line script and a template.pto.
suddenly we have 2 places of vignetting, one at the edge and one
opposite to the middle, since both original images have vignetting.

with help i tried different approaches on reducing this automatically
with imagemagick, but due to light differences between shots, clouds and
so on, we didn't get it working properly.
although some methods of remapping mean values did reduce or remove the
dark band it also created strange light effects and color changes on
other occasions.

the only thing i could come up with it training an AI to recognise the
specific region where it might occur, but that would take up too much
resources to train for me :)

my question, does anybody have a working solution for targeting this
problem?
or should i just let it go.

Maarten

[Maarten Verberne]

i forgot to add an example :)

Op 05-Jul-23 om 21:37 schreef Maarten Verberne:

[Bruno Postle]

Are both photos taken at the same time? I'm trying to figure-out the intent.

If you just want an even blend across the sky, then you can increase the number of levels in the blend pyramid to the maximum. In the Stitcher tab, set enblend options to -l 27

-- 

Bruno

[Bruno Postle]

Yes, something like this (all on one line, Google will mangle this email):

  enblend -o project.tif -l 27 project0000.tif project0001.tif

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Bruno

On Wed, 5 Jul 2023, 21:51 Maarten Verberne wrote:

yes, they are taken at the same time, but i have a series of these, so
the dark part changes over time and gets clouds a few minutes later.

can i test that in command line and if so how should i add this to the
example?
enblend -o project.tif project0000.tif project0001.tif

Op 05-Jul-23 om 22:27 schreef Bruno Postle:

[Bruno Postle]

Enblend will adjust areas that are outside the overlap, -l 27 just tells it to use the maximum number of levels possible.

Hugin can correct 'normal' radial vignetting, but these shots are not ideal for calibration. You would need to shoot a simple scene with about 50% overlap, get Hugin to optimise photometric and vignetting and save these parameters to apply to your sky shots.

-- 

Bruno

On Thu, 6 Jul 2023, 12:00 Maarten Verberne wrote:

Sorry, but i didn't explain properly.
the seam on the image is bright and nice, the dark vignetting is the
part that isn't blended on the original image.
since enblend already takes highest level of pyramids as default, adding
-l 27 only gave me that it was too much and that it would lower to 10

to make it work for my purpose it needs to remove the vignetting next to
the seam or remove the vignetting on the original image before enblend
has a go at it.

[Greg 'groggy' Lehey]

On Wednesday, 5 July 2023 at 22:47:00 +0100, Bruno Postle wrote:
> Yes, something like this (all on one line, Google will mangle this email):
>
> enblend -o project.tif -l 27 project0000.tif project0001.tif

Is this documented anywhere? I see a brief mention of the syntax on
the man page, but not what it really does.

Greg
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[Maarten Verberne]

i also had a bit of trouble finding the documentation of this, but it's
the pyramid levels...or how many triangles should enblend use.
as i found it appears that enblend by default takes the highest possible
setting for this.


Op 07-Jul-23 om 6:58 schreef Greg 'groggy' Lehey:

[Bruno Postle]

The man page isn't very clear, enblend looks at the overlap size and sets the number of levels to mostly sample from the overlap area. If you set it to a large number of levels it will sample from much further beyond the overlap area - which is useful for smoothing out a sky.

-- 

Bruno