Handheld Shooting Guidelines for Panoramas
You can easily get a good stitch with handheld panos if there aren't any
important features close to the camera. Objects closer than about 30 feet
are at the most risk of parallax error, where features move from shot to
shot and no possible stitch can line everything up. Farther than that, and
the effect is generally small enough to get a good stitch.
If you've shot a handheld panorama and you want a good stitch, choose control points that are far away. If you use autopano or another automatic control-point picker,
look to see what control points it chose and delete the
ones points that are in the foreground. Manually add some more control points in the distance
if needed. Then you'll get a decent stitch without the optimizer trying to do
the impossible. Those parts of the picture that are in the foreground
might be doubled or won't line up, but in a field of grass or on a sandy beach
that can be hard to spot.
When near and far objects don't line up during stitching, it's because of
"parallax effect": the camera wasn't in exactly the same spot when the two
pictures were taken, and this causes near and far things to "move" relative to
each other.
The usual (wrong) way to shoot a panorama is to stand in one spot and rotate
your body from shot to shot. When you do this, you are holding the camera in
front of yourself a little bit and turning your body. This means the camera is
moving in space, describing a circle around where you're standing. To get
better results, instead of turning your body,
turn the camera. Identify a spot on the ground, hold the camera over that spot, and
shoot your first picture. Then for the next picture, rotate the camera while
still holding it over that spot. As you shoot, you'll be doing a little dance
where the camera stays in one place and you orbit around it. This will give a
lot less parallax - the camera doesn't move so much between shots.
When referring to the camera being in "exactly the same spot," you should
ask, "Which part of the camera has to be in the same spot?" That's a key
concept for minimizing parallax and getting really good stitching with nearby
objects. The camera should rotate around something called its "pivot point" - a
kind of "optical center" of the camera and lens system. (Some people say "nodal
point" but there is at least
one paper online
that disputes that terminology. So let's just call it "pivot point.")
If you rotate the camera around its pivot point, you won't get any parallax:
near and far objects won't shift in relation to each other from one shot to the
next. The pivot point is the spot that to be held in a fixed position in space -
don't let it move up or down, left or right. Your goal is to find that point and
keep it fixed in space as you rotate the camera around to shoot multiple shots.
A "panorama head" will do this. After determining the pivot point for your
camera, you adjust the pano head appropriately and mount your camera in it. Then
you put the pano head on your tripod. As you pan around in a circle, the pano
head causes the camera to rotate around its pivot point. To shoot multiple rows,
you have to tilt the camera up & down inside the pano head - the tripod's tilt
system will not tilt the camera around the proper center of rotation.
For ultra-compact cameras, sometimes you can get away with something simpler.
I built a little L-shaped bracket that would hold my camera sideways (in
portrait orientation). I found I could mount the camera to the bracket and the
bracket to a tripod, and the two rotation axes intersected very close to the
pivot point. That is, I could tilt the camera up and down in the bracket and
rotate the bracket around on the tripod head and get quite an acceptable
full-sphere indoor pano.
The bigger the camera (that is, the longer the lens), the more you'll need a
real panorama head. If you make your own bracket, be sure to align the tripod
mount screw hole under the lens, which isn't always in the center of the camera
body.
Also consider a "Philopod."
A Philopod is a virtual monopod that helps you keep the camera over one spot on
the ground as you shoot. It's just a string with a weight tied to the bottom.
You tie the string to the lens at the proper pivot point, which is generally
between the camera body and the front opening of the lens. (Actually, tying it
anywhere on the lens barrel will probably be better than trying to shoot
with no assistance at all!) It's a cheap and compact way to help you rotate the
camera around its pivot point and also helps you avoid drifting up, down, left,
or right between shots. With it, you can get good indoor panos or outdoor ones
with nearby objects. Just a little assistance can be a big help - you usually
don't need to be perfect to get a decent stitch. You'll find more about the
Philopod and panorama photography generally at philohome,
Philippe Hurbain's homepage.
The same PDF paper referenced above about nodal points describes a way to
find the pivot point of a camera and lens system, regardless of what bracket or
assistance you're using. Here's a quick version:
Find a place where you can see a nearby fence post maybe a yard or two away
and a distant tree many yards away. Stand so the post lines up in front of the
tree. Use your camera to frame the post-and-tree through the viewfinder so
they're on the left side of the image. Now rotate the camera so you see them at
the right side of the image. If the post still lines up with the tree, you've
rotated around the camera's pivot point. If the post shifts left or right
relative to the tree, you haven't found the right center of rotation. You need
to adjust things and try again. (With the string trick, slide the string closer
to the camera body or farther away. With other systems, do a similar in/out or
left/right adjustment.)
For multi-row panos where you tilt the camera up and down, the string trick
can still do an OK job. Your axis of tilting will be the knot just below the
lens, not really inside the lens body where the pivot point is. But you might be
close enough to get good stitches. After all, how often do you shoot a pano when
there is a fence post just three feet away?
Don't obsess about the near field when the main points of interest are
farther out. If you shoot a business complex from a parking lot in the center,
the people looking at your pano might not care if the nearest cars look a little broken.
Other contributors to the Google group on Panorama tools wrote:
You may want to check out these do-it-yourself pano heads
here and
here and
also what the author did for himself
here.
This page was last edited
April 26, 2008. |