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Hack 82 Get the Big Picture with a Little Camera Phone

If a scene is just too big to fit in your
little camera phone, shoot a series of images and stitch them
together.

Have you ever photographed a breathtaking
landscape or something extremely
tall, such as a giant redwood or skyscraper, only to feel a little
disappointed when looking at the image on the computer screen? The
scale of the scene didn't survive the translation to
the computer.

One reason is that the conventional camera has a monocular
field of view, which is much smaller than
the stereoscopic
field of view that our two eyes provide.
This issue is compounded by the camera phone's
generally low resolution (sub-megapixel) and narrow depth of field;
objects are not sharp, except for a narrow range of distance from the
camera. You also might not be able to back up far enough to get a
large vista or object entirely in a single frame.

One way to solve this problem is to photograph the scene or object in
segments and then assemble the pieces into a single large image. The
technique, called a panorama [Hack #19], is pretty simple. Figure 7-14 shows three pictures stitched together into
one.

Figure 7-14. A panorama created from three camera-phone images

Here are a few tips to keep in mind
when you're
creating these types of images:

Decide which kind of panoramic image you want to create. The two most
likely choices are horizontal and vertical.

Some digital cameras provide on-screen tools to help you line up
stitched images as you're shooting them. Camera
phones, however, do not have this feature. You can work around this
by visually scanning the area you want to photograph and choosing
visual segmentation points to help you line up the photographs and
create assembly segments. The rule of thumb is to overlap each frame
by 30%.

Camera phones
don't have sockets that you can attach to tripods to
ensure smooth panning. So, this is hand-holding country. To produce
the best results, minimize your body movement when
you're photographing each segment. I recommend
keeping your feet in a single spot throughout the entire process.
Twist your waist, while keeping your back as vertical as possible,
for horizontal panorama scenes. When photographing vertical scenes,
try to bend your shoulders and waist straight back (when shooting
upwards) or forward (when shooting down). These behaviors minimize
segment mismatches that create unusable visual areas.

Bring the photo segments into a photo-stitching (sometimes referred
to as photo-merging) application. A
number of general-purpose, commercial photo-editing applications
include photo-stitching tools, such as Photomerge in Photoshop CS and
Elements.

Standalone photo-stitching tools, such as ArcSoft PanoramaMaker (http://www.arcsoft.com/en/products/panoramamaker/),
are also available. For this project, I used the PhotoStitch
application that came bundled with my Canon PowerShot G3 digital
camera. You can also find open source photo-stitching tools
associated with the Panorama Tools project (http://panotools.sourceforge.net/).

Most applications automate the bulk of the actual photo-stitching
process. However, there are usually options to adjust for different
ways of producing and merging segmented images. You should experiment
with these different methods to learn which ones work best with your
photographic technique.

I'll now walk you through the basic steps of
creating a panorama with your camera
phone. First, take your series of shots, working left to right and
overlapping by 30%. Upload the pictures to your computer. Open the
images in your stitching program, as shown in Figure 7-15.

Figure 7-15. A series of shots in Canon's PhotoStitch application

Now, merge the images together, as shown in Figure 7-16. If you give the stitching application enough
visual information to work with, it will do an amazing job of
creating a seamless panorama.

Figure 7-16. Photos being merged together

Once the application works its magic, you have a much broader view.
Crop out the rough edges, as shown in Figure 7-17.

Figure 7-17. Cleaning up after the merge

A bonus of using this technique is that you've also
added resolution to your landscape, which enables you to make a
bigger print than you'd be able to make of a single
640 480 picture. You don't have to be limited to
small prints or narrowly composed scenes with your camera phone. Just
remember to gather all the parts while you're taking
the pictures. Then, pull things together later on the computer.
It's that easy.

Todd Ogasawara