Erik Krause 2009-Dec-10 23:39:16
A multi viewpoint, three different focal length, handheld spherical
I didn't plan to make this one. It was just an experiment, from multiple
points of view (literally ;-)
Me and my family climbed the Sidelhorn near Grimsel pass in Switzerland
this summer (the kids had much fun searching for quartz crystals) and I
had my usual camera rucksack with me - no pano head, no tripod. From the
summit there was a magnificent view all around, with two of the most
impressive mountains over 4000m in the Bernese range (Finsteraarhorn and
Lauteraarhorn), the Matterhorn far in the dust and the Furka Pass, Uri
granite mountains and the Rhone glacier in the east. And a view down in
the upper Rhone valley (called Goms), to the Aare glaciers and lakes.
So I took a two row 360° panorama at 50mm from four different viewpoints
around the summmit in order to avoid having the mandatory cross on the
summit in the image and to view down in all adjacent valleys. I thought
of something similar to those "from the tower without the tower" panos.
Because the sky was so nice I took an additional 360° cylindrical from
the sky just above the mountains at 24mm focal length. I planned to make
a high res cylindrical of the 50mm and 24mm images.
And because it was so nice I took an additional complete spherical with
the 16mm fisheye, bracketed -2, 0, +2...
Month later when I was at my parents during autumn holidays I had
nothing to do, but I had an old 2.4GHz 512MB notebook and the external
disk with all the images from summer with me. So I set up some PTGui
projects. It turned out that one exposure step from the fisheye was the
same as the exposure I took the rectilinear images, and so I got curious
whether it was possible to stitch the fisheye and the rectilinear images
together and how far I would get with this tiny machine.
For ease of use I converted all images from raw to jpeg but with full
resolution (20MP) and maximum dynamic range. To my suprise it was
possible to load all 82 images into PTGui and align them. After some
playing with blend priority the preview in pano editor looked pretty
promising. I didn't dare to actually stitch, since PTGui reported that
118 GB temp space where needed and the internal hard disk is 20 GB only.
But now I wanted to make it, on my old machine at home or on a new one
which I wanted to buy anyway.
When Max Lyons published the first gigapixel in 2003 my computer at home
was already three years old and I thought I would never ever stitch a
gigapixel on this machine. Max reported two days of optimizing. Well,
PTGui took some minutes only to optimize the project on the poor
notebook and not far longer on my computer at home. It was a challenge
for my old Athlon 1.4 GHz, 1.5 GB - if it failed, there would be a new
computer in several weeks...
I optimized all images together. Actually I had to set several control
points manually between the different focal lengths, but after some
iterations it optimized well. Then I split the project in three, one for
each focal length. I stitched the two lower resolution ones to their
recommended maximum size, and the high resolution one consisting of 62
images to 46,000x23,000 pixel (maximum would have been 52,000x26,000).
Stitching was ready after 14 hours (I was prepared to cancel the job
after 36 hours) and delivered a 10 GB .psb file, containing the blended
panorama and all individual warped images, which I needed to retouch
huge parallax errors because of multiple viewpoints. So next came
photoshop - would it open the file? Yes, it would.
It took about 1 hour to load, but working the masks with the brush was
relatively fast. Flatting the image took more than an hour as well as
saving the edited .psb.
When all three panoramas where more or less ok, I loaded them all in
PTGui again in order to blow the lower resolution ones up and take
advantage of blend priority and the PTGui blender. Processing took about
12 hours again. Result was 8GB large (3 layers + blended) and took about
the same times to open and process in photoshop.
During retouch work I discovered, that PTGui blender did a poor job on
slight parallax errors in the high res version (structure doubling along
the seam lines, which I know from ancient PTStitcher feather blending).
So I decided to give enblend a chance. For this purpose I merged
non-overlapping images into single layers. 62 layers where reduced to 7
with the hope to speed up enblend. The -a switch does the same and
usually speeds up enblend a lot. My assumption was that pre-assembling
images would speed it up even more.
Enblend 3.2 crashed with an out of memory error, which is possibly the
documented memory leak in this version. Enblend 3.0 succeeded after one
night of processing and delivered a nice blended result almost without
the double structures. I replaced the respective layer with the enblend
result and could focus on the blending between the different resolutions
After some adaptive contrast enhancements (large radius USM took about 2
hours to complete and 1 hour "prepare to filter" on each layer) and hour
long saving I had no chance to view the full resolution version locally
on my computer. DevalVR refused with out of memory. I had to scale down
Then I started FTP upload to 360cities, which took 7 hours. Next morning
I had the first view and a shock: There was I white stripe in the pano.
No, it was not 360cities image processing, it was me.
Searching back through the different versions was pretty tedious - any
one took ages to load, but finally I found a stripe free version. The
cause for the stripe must have been a layer copy in photoshop with shift
key released too soon.
In the 3 hours I had each day there was hardly time to load the .psb, do
one operation and save again. So it took another week until I had
re-done the necessary editing and fixed some more stitching errors.
Ah, ok, the URL, finally. Have fun:
Who ever finds a stitching error can keep it for better days ;-) There
surely are a lot more than I fixed. I'm not very satisfied with the
transition between high and low resolution in some places while in other
places it looks quite ok - but I hope no casual user will look down
hires on boring stones...
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