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Chapter 9: Airbor ne V ideo Systems 237

There is also the issue of choosing FOV versus close-up details, often referred to as
telephoto. In Figures 9.7 to 9.11, you will see the series of photos I made in my back
meadow. It illustrates the tradeoff between using FOV or telephoto with a Canon DSLR
camera fitted with an 18- to 270-mm telephoto lens. The focal length is the only variable
that was changed in each of the photos to illustrate how the FOV rapidly reduces as the
focal length increases.
You can clearly see from this series of photos that the detail rapidly diminishes as the
FOV expands. Figure 9.12 is another interesting example of this effect. It is an evening
cityscape of Vancouver, BC, courtesy of Snapshot.com and photographer Darren Stone.
The Hero 3 optical system does not have any physical means to alter or change the focal
length; hence, the optical FOV is fixed. It can, however, alter the FOV electronically by
selecting different areas of the imaging sensor and expanding the selected pixels to fill the
total image. This feature is shown in Figure 9.13, which shows the same scene taken on a
Greek island in wide, medium, and narrow FOVs.
I next decided to test the Hero 3 camera to see how it handles very close-up photography.
I used the classic Indian-Head test pattern that was widely used in the early days of
monochrome, or black and white, television of the 1950s. This pattern is shown in Figure 9.14.
I took the photo shown in Figure 9.15 with the front of the Hero 3 lens only 4 cm (1.6 in)
from the test pattern. You can clearly see the severe barrel distortion that happens when a
Hero image capture is taken very close to the camera. The distortion lessens considerably as
you separate the camera from the object being photographed. I also used the Adobe
Photoshop lens-correction tool to see if the photo distortion could be somewhat mitigated. It
was, to a small extent, as you can see in Figure 9.16.

Figure 9.7 Focal length of 18 mm.