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Hack 95 Advanced Panorama Technique

Once you've played a bit with
panoramas, you might want to raise the bar and produce
professional-quality images. Here are some secrets the pros
use.

[Hack #19] discussed the
basics of capturing photos to be
stitched into panoramic images, including putting
the camera on manual exposure, using a fixed white-balance setting,
and maybe even using manual focus. One trick you might not be using
to broaden your shots is turning the camera vertically. Though
you'll have to take more shots to span the same
180° scene, you'll capture more height in
your composition.

When positioning the camera, it's import to keep it
level. If your horizon is flat, you can use it as a guide. Better
yet, you can use a hot-shoe level [Hack #9] where your flash would
normally go. Once the camera has been leveled, don't
continue to fiddle with its alignment; you'll have a
harder time stitching the images together on the computer.

8.11.1 Avoiding Parallax

One of the most important terms related to panoramic photography is
parallax.
Parallax is the very thing that gives humans depth perception, but it
is the enemy of panoramic photography. Here is a demonstration of
parallax. Hold your finger out at arm's length;
first close one eye, then the other. You finger moves relative to
objects in the background. This is how we perceive depth. Now, while
your hand is still out, close one eye again and this time rotate your
head. You notice that your finger still moves relative to the
background. This is because you rotate your head around your neck
rather than your eye. If you were able to rotate around your eye,
your finger would not move relative to the background.

When taking panoramic photographs, your goal is the lack of a
parallax when you rotate the camera. It's not really
an issue if you are shooting a distant landscape without any
foreground objects, but as objects get closer, minimizing the amount
of parallax (known as the parallax error)
becomes more important.

So how do you avoid parallax? Well, every camera has an axis point
beneath the lens (commonly referred to as the nodal
point) around which you can rotate the camera to avoid any
parallax error. This point is typically inside the lens. Once you
have a method for holding the camera, you can use a little trial and
error to hone in on just the right spot. I'll
describe a technique for this later. Don't worry
about perfection on this; for most shots, you don't
have to be perfect, just in the ballpark. However, if you are
shooting in a small, confined space, such as a car or small room, you
want to put some time into finding the nodal point.

One option for successful camera rotation is to use a high-end,
professional panoramic head. These are stable and easy to work with,
but they're also expensive and heavy. Many of the
companies that offer high-end panoramic heads also build entry-level
models that are more in line with a typical
consumer's budget. These panoramic heads mount the
camera vertically and then offset it back and to the side so that the
nodal point is over the center of the tripod. They also click in at
set increments as you rotate, making it easy to get shots at equal
spacing. For example, every 45 degrees might result in eight shots
for a full 360-degree circle.

So, you're not ready to buy one of these? No
problem; you can still capture excellent panoramas without one. Even
the pros who use the high-end panoramic heads still find themselves
in situations where they want to shoot a panoramic photo but
can't drag all the equipment along.

8.11.2 Expert Hand-held Panorama Technique

When shooting
panoramas, the natural tendency is
to rotate around your heels with the camera out in front of you;
however, you should not do this. As shown in the right half of Figure 8-25, when you rotate around your heels, the camera
lens circumscribes a large circle.

Figure 8-25. Proper handheld panorama technique

This is bad because the nodal point in the lens, represented in Figure 8-25 as short black lines, is nowhere near your
center of rotation. Because of this, you have introduced a parallax
error, just as you did when you turned your head with your finger
out.

Instead, you should keep the lens position stationary, as shown in
the left half of Figure 8-25. Stand with your left
foot forward and right foot back. Place the ball of your left foot
directly under the camera lens. Play around with your stance and the
spread of your feet until it feels comfortable. Then, rotate around
the ball of your left foot. The camera lens should stay at the same
spot, while your right heel makes a circle.

8.11.3 The Cardboard-Tube Cradle

I have come up with a solution that is somewhere between hand-holding
and using a full panoramic tripod head. This technique
is ideal to use with a monopod and is best described as a
lens cradle. I don't want to
use the word mount, because
the camera is not really mounted to the cradle; it just rests there,
as shown in Figure 8-26. When using the cradle, I
recommend you keep a hand on the camera and keep the neck strap
around your neck.

Figure 8-26. Cardboard-tube cradle

The only raw material you need to build this cradle is a tube. I used
a heavy-duty cardboard tube, but I don't see any
reason why you couldn't use PVC or some other
material. The tube should have a diameter of roughly three inches.
For tools, you'll need a knife or saw to cut the
tube, and a drill with a 3/16" bit.

Here are step-by-step instructions for how to assemble the lens
cradle:

Find a tube that fits the specifications described previously. It
should be thick; otherwise, you will have to layer and glue a few
pieces together.

Cut about a 1.5-inch section off the tube. Then, cut that section in
half so that you have two pieces that each look like a C.

You will likely want to layer these pieces and glue them together, as
shown in Figure 8-27, to make the cradle more rigid
and thick enough that the tripod screw won't poke
through the top. If the material is thick enough, you might be fine
without layering.

Drill a hole in the center of the C to mount it to the monopod or
tripod. I used a 3/16" drill bit. You might need to go bigger than
this, depending on your tube material.

Figure 8-27. Gluing together layers of your cradle

Once you screw the tube onto the monopod, you're
ready to go. Turn the camera sideways, rest the lens in the cradle,
and shoot. You should focus ahead of time because the cradle might
interfere with focusing, and you should also take care to keep the
monopod level. Mounting a level on the monopod, as shown in Figure 8-28, can make this easier. Also make sure that the
camera is level in the cradle, not tilted up or down.

Figure 8-28. Bubble level attached to a monopod

So, now that you know how to rotate around the nodal point, how do
you fine-tune the location of the nodal point for your lens?
Basically, it's done by trial and error. Set up for
a panoramic photo in a location where you have one vertical element
close to the camera and another vertical element off in the distance.
Place the camera with just a sliver of space between the two vertical
elements. Rotate the camera to the left and then to the right. If
that gap does not disappear or grow, you are right where you need to
be. If the gap does change, try sliding the camera forward or
backward in the cradle. If it gets worse, you went the wrong way or
just went too far. Just keep adjusting with small moves until you are
happy with the results; then make a mark on the cradle for future
reference. Keep in mind that the nodal point of a lens will change as
you zoom your lens, but most of the time, you will be shooting
panoramic photos at the full, wide setting of the lens.

Perfecting your panoramic photography skills takes a while, but
putting in the time up-front to learn how to get the best photos will
save you time at the computer and give you a better photo in the
end.

David Goldwasser