I'm trying to fuse exposure stacks, following what I
understand from the tutorials and these recent posts,
without success; so I'd be really grateful for some newbie
advice. I'm using Hugin 2011.4.0cf9be9344356 in Linux Mint
Debian.
I've a set of 5 hand-held images each at 3 bracketed
exposures, taken with the AEB setting on the camera (to
minimise movement between shots).
The images are set up as 5 stacks with unlinked images; the
control points found with CPfind Multirow/Stacks; alignment
optimised for y,p,r,x,y,z; then stitched with exposure fused
from stacks.
The result is fine towards the edges of the panorama, but in
the centre the stack(s) is/aren't properly fused - both
foreground and distance are out of register.
It's not resolved by anything I've tried - unlinking the
lens, assigning different lenses to the stacks, etc.
Where am I going wrong?
Could parallax between adjacent images in the centre of the
picture be causing problems? What could I do about it, if it
were?
Doug
On 23/12/11 09:06, kfj wrote:
On 23 Dez., 03:42, Calvin McDonald<[email protected]> wrote:
Thanks for the help Kay.
After 5-6 failed attempts trying to exposure-fuse within Hugin, I'm now
trying image-set by image-set with command-line enfuse.
I'm getting pretty good (acceptable) exposure-fusing results via
command-line, so I'm encouraged. However, I'm on to the next problem....
alignment. I know better now but when I took the image-set I made the
mistake of not taking the two exposure shots back-to-back. I took the 12
upper row shots at exposure setting #1, then went back and took the 12 with
the alternate exposure. Although tripod mounted with a nice detent pano
head, it of course didn't create perfect alignment between the image
pairs. The alignment error is about 20 or so pixels - just enough to make
the transition from land to sky look horrid.
How do I align them?
You should be able to do it all in hugin. When you say your attempts
failed, what went wrong?
There is one common mistake in your situation. I suppose you still
have your initial attempt with all the images in hugin. Since your
stacks are not perfectly aligned the way you took them, you have to
uncheck the 'link' checkbox next to the image position fields in the
images tab for each of your misaligned stacks. If you don't do that,
the stacked images will be placed precisely on top of each other and
their positions will be linked, and it sounds as if this was happening
with your panorama.
You need control points between the images in the stacks in order to
align them, so in case you don't have them (linked stacked images can
do without control points), you'll need another run of a control point
generator - align_image_stack is popular for the specific case, but
cpfind with settings to create a few more points than usual (try --
fullscale --sieve2size 5 -o %o %s) works well, too - and another
optimizer run.
Once everything is optimized, the minor shifts between the stacked
images should be dealt with and you can proceed to let hugin create
the fused panorama. You can check the quality of the alignment in the
preview by setting the viewing mode to difference in the preview tab
of the preview. If the overlap is generally very good, instead of
creating a panorama from fused stacks you can also try and go the
other way by creating an exposure fusion from an arbitrary
arrangement, which has the added benefit that it lets you keep the
intermediate layers to blend yourself if you want.
Do trials with small output sizes to see what looks about right, then
when you think you're getting there, crop out a typical section and do
it higher-res, then when all seems fine have a go at the full pano.
Sadly I couldn't find a way to make hugin keep the fused stacks before
feeding them to enblend, which would be nice for you to play with (am
I blind? or is there really no such option?). What you can do, though,
is keep all the remapped images (no photometric correction, LDR) and
enfuse them manually. They should be well-aligned now they have been
made from unlinked stacks.
If you're on windows, there are also the enfuse-align droplets, where
you can just drag and drop sequences of images onto them and have an
exposure fusion made from an aligned unlinked stack. This might be an
option if you want to manually enfuse but not use hugin for it.
And I'm sure there are many more possibilities... it's confusing at
first, but you'll get there ;-)
Kay
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