Canon Camera Hackers Manual page 208

images precisely, especially when shooting panoramas hand-held: Edge
overlay shows the edges of the previous image on top of the current
viewfinder content (section 4.7 and
Stitching programs usually accept TIFF and JPEG files. Shooting JPEG is
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just fine. If you want to use RAW files for the ultimate quality, make sure
you have enough space on your memory card. Also make sure to de-
velop each RAW file with exactly the same parameters.
After you create a series of panoramic shots, you will need to stitch them
together. There are several programs that can help you in that task. These
programs differ in details, quality, and level of manual control but more or
less keep to the same process:
1. The program searches for prominent points within the single images
(using the SIFT algorithm or a similar algorithm)—points that clearly
stand out and can be used for registering images.
2. The next step is to match the points from the single images. This is
usually done with the RANSAC algorithm. Most of the stitching pro-
grams are able to accept an unordered set of images and will put them
into the right sequence.
3. The single images are shifted, rotated, and stretched to make them fit
together.
4. The single images are further corrected by removing the effects of vi-
gnetting (lens shading), barrel and pincushion distortions, and different
exposures.
5. The single images are fused together. This happens within the overlap-
ping area by choosing a (usually irregular) borderline that is not too
obtrusive. The transitions are softened up, and ghosts within the transi-
tion area are masked out.
There are many commercial panorama stitchers but also some very capable
free programs:
First, Photoshop offers Photomerge, an easy-to-use panorama stitcher.
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It's a tool for the quick panorama without too many configuration op-
tions. It's free, too, as long as you own a Photoshop license.
The Microsoft Image Composite Editor (ICE) is similarly easy to use, and
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it's completely free.
Autopano Pro from Kolor is a very powerful panorama stitcher. Panora-
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mas can be created automatically, but you also have full manual control
over each step. The program can keep the whole contrast range deliv-
ered by the single images and allows storing the panorama as an HDR
file. It can even combine several HDR stacks, resulting in true HDR pan-
oramas (section 4.6.2).
Figure 4-40).
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6.1 Panoramas