202 CHAPTER 6 Advanced Techniques
cameras: the lack of interchangeable lenses. Most compact cameras allow
for a wide-angle zoom position of 35mm focal length (35mm equivalent),
some even down to 28 mm. But when compared with the ultra-wide-angle
lenses available for DSLR owners (24 mm down to 12 mm equiv.), one can
only feel envy.
With panorama techniques, you can simulate an ultra-wide-angle lens.
Instead of using a cylindrical projection, you use an equilinear projection
when stitching the images. The image in Figure 6-1 consists of nine single
shots, three shots in three rows. The camera was a Canon Digital Elph
SD1100 at a wide-angle setting (equiv. 38 mm). Because the contrast range
was rather high, I decided to use HDR bracketing as well, with three images
per shot, and a Tv Bracketing value of 2 EV. This resulted in 27 single images.
In such a case, you should consider selecting the next lower image reso-
lution. Some HDR tone mappers cannot handle images that are too large,
and processing times can become excessive. The images delivered by the
panoramic stitcher can be very large, indeed! Because I had taken the im-
ages at full resolution, I scaled them down afterwards to 1600x1200 pixels.
The images were then composed in Hugin with virtually no manual adjust-
ments. The only thing I had to do was supply a format factor of six manu-
ally. (Hugin proposed a wrong format factor because of the extra scaling
process.) Also, I set the projection to rectilinear, the exposure optimization
to HDR, and the output format to HDR. The resulting image had a horizon-
tal angle of 125° (145° in the diagonal). The simulated focal length was
7 mm (35mm equivalent), a value DSLR owners can only dream of. The re-
sulting EXR file was then opened with Picturenaut and tone mapped using
the bilateral method.
Figure 6-1
Breuburg Castle, Germany.
Even after some heavy cro pping,
the image still has a horizontal angle
of 88° (98° in the diagonal).
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