PanoTools:
Re: Need help stitching my helicopter panorama!
superpanoramas 2005-Jun-05 00:07:17
Hi Ed,
As already said by others, the parallax error (and also the
difference in viewpoint) is too big for these images to be
sitichable. The main rotor also got in the way causing "blackouts" in
the sky, but this can be fixed in Photoshop.
So, unfortunately (or fortunately, depending how much you like
flying) you will have to go back in the air if you want to get this
one right. Not to repeat what was already said, but to add some more
obvious things you can do to get it right next time:
1. Take more pictures. Simply, while in the air, take as many
pictures as possible, as fast as possible. If you set your exposure
and focus correct, then the only thing you have to worry about is
what ends up in the frame. If the pilot can't keep the heli really
steady (which is actually very, very hard to do, even for experienced
pilots) the only thing to do to handle that is to shoot real fast so
the parallax error doesn't get as bad as it has in your shots.
2. Use way more overlap than you think you will need. Especially with
a fisheye which has a tremendous field of view, you may want to use
as much as 50 or even 70% overlap, since you are loosing sharpness
and pixels (due to the sides having to be stretched out) real fast.
3. Do it more than once. Air time is expensive, and the old
saying "film is cheap" is even truer with digital. If you carefully
plan out with your pilot what you want to do, instead of waiting
for "the perfect moment" to shoot, take the biggest memory card (or
microdrive) your camera will take, and keep shooting from the moment
you first get into position until you head back to the heliport.
Don't wait for the perfect perspective. If the pilot is just getting
into position, do a series, then do another when he is in position.
Once you are happy with your shots and think "you've got it", just
start right over and keep shooting until your airtime runs out. I
know exactly how it feels when you think you are done and think you
have the shots you need in the bag - that's the time to continue as
long as you can (that is, as long as you are up in the air).
4. Direct the pilot so he knows what you need and what is important
for you. He needs to know that if the heli moves too much
horizontally (i.e. forward or back if you are shoting sideways) your
shots won't work, so he can favor correcting in that direction. If it
is skidding sideways in one direction or the other, that's not that
bad since you are very far away from your subject(s), but if the
perspective changes, you won't have a pano that can be stitched.
Assuming you are shooting sideways, skidding sideways (so you get
closer or further away from the imagined point in the middle of your
viewfinder) is not likely to cause much of a problem, skidding
forward or backward is what you have to watch for as this can't be
corrected in stitching since as your viewpoint (and thus the
perspective) changes, the place of certain objects will change IN
RELATION to neighbouring objects, e.g. a building that was on the
right of another will be behind it in the next shot. There is no
stitching "trick" that can handle that. This is the cause of your
double towers. So make sure your pilot knows this is what he/she will
have to watch for while trying to hoover.
I hope this helps.
Robert Palinkas
http://superpanoramas.com
Panoramic & Super-High Resolution Photography
--- In #removed#, "Edward Fink" <#removed#> wrote:
> I could use some help if anyone has the time to try stitching
> some aerial photos to see if I'm doing something wrong.
>
> I shot my first panoramas from a helicopter Tuesday, but they
> have so many stitching errors that I'm about to trash it all and
reshoot
> everything.
>
> It was probably too windy that day. We even had to start over
> once because we drifted a couple of blocks down the street between
the
> first shot and the second.
>
> My client is trying to talk the pilot into a half price charge
> for the retake, but at this point I can't be certain that I'm not
doing
> something wrong. I did shoot down at a -30 to -40 degree angle,
trying
> to use the good part of the lens more, and trying to get lots of
overlap
> for the nadir, which isn't normal for me, but I don't think that
would
> cause the problem.
>
> It looks so bad that I haven't even tried to warp things into
> place with Photoshop yet. I've been so spoiled by my Kaidan Quick
Pan
> III that I've never had to deal with anything this far out of whack
> before, so I'm looking to see what I can do to improve it in PTGui
> before using Photoshop. (Especially since I also shot panoramas
over two
> other cities, and those look just as bad as the first one.)
>
> I was surprised to find that even with dozens of control
points
> per seam and control points on the horizon on all four pictures, the
> horizon still got pretty screwed up. It was so bad that I finally
> stopped optimizing and just typed in all the pitch and roll values
to
> level the horizon. I could get a really nice straight horizon that
way,
> but some buildings end up being misaligned so bad they're a block
or two
> away from where they should be. I've got twin towers where there
should
> only be one.
>
> The four JPG's from my Nikon D70/Sigma 8mm are at:
> http://www.new-eden.com/temp/Minneapolis.zip
>
> The VR that I get from them, straight out of Enblend, is at:
> http://www.new-eden.com/temp/MINNEAPOLISSKYTOUR.MOV
>
>
> Ed
> #removed#
> http://www.new-eden.com/
> No eternal reward will forgive us now for wasting the dawn.
> -- Jim Morrison --
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