Bracketing; General Bracketing Notes - Canon Camera Hackers Manual

The functions Average, Sum, and Develop can also be invoked program-
matically via a Lua script (section 5.5.9), which allows automating such
superimposition tasks completely.
4.6

Bracketing

Bracketing is a camera function that produces a series of photos with vary-
ing settings. Traditionally, bracketing was used to obtain an image with
perfect exposure. First, an image with the measured exposure was made,
then an image half an f-stop overexposed, then an image half an f-stop
underexposed, then the same with a full f-stop. Even analog cameras had
the ability to perform bracketing in an automated fashion—which wasted
a lot of film.
Today, with digital imaging, bracketing can still be used to obtain a
perfectly exposed picture. It also has found new applications [Gulbins2009].
Combining the different pictures of a bracketing series into a single image
has become quite easy, and new algorithms for image processing provide
results that analog photographers can only dream of.
The traditional exposure series can now be used to combine the differ-
ently exposed images into a single image with a wider dynamic range. This
type of photography—called High Dynamic Range ( HDR) photography (sec-
tion 4.6.2)—has become fairly popular among serious amateur photogra-
phers. The results often resemble a painting rather than a photograph.
During post-processing, you have many options for compressing the huge
dynamic range into a smaller and printable (or viewable) dynamic range. It
is certainly a matter of personal preference and taste as to how the results
will look.
Exposure values aren't the only items that can be bracketed; the same
is possible with focal distance. Starting from a measured or manually set
distance, the camera can make exposures with longer distances and
shorter distances (section 4.6.3). Later, during post-processing on a PC, the
images can be combined with the help of a special focus stacker. These
programs select the sharpest parts of each image and combine them into
a single image. The results are images with an extended Depth of Field
( DOF). This technique is typically used in macro photography where the
depth of field is very small.

4.6.1 General bracketing notes

Setting up the camera for an unlimited series of bracketing shots is very
easy under the CHDK. Just go to the Bracketing submenu and set the values
for the entries found there:
4.6 Bracketing
Figure 4-38
The Bracketing submenu is reached
via ALT > MENU > Extra Photo
Operations > Bracketing in Continuous
Mode. Here we see a typical
configuration for shooting
HDR images.
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