Time Machines - Canon Camera Hackers Manual

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C H A P T E R 5 Scripting
for creating time-lapse series, very often time-lapse movies. Bracketing
scripts are used for creating High Dynamic Range ( HDR) photos or for creat-
ing images with extended depth of field via focus stacks. Finally, motion
detection is used for all kinds of purposes: lightning photography, surveil-
lance, wildlife, and more. For example, I found it good fun to set up the
camera at a party, load a motion detection script, and let the camera do the
work. The resulting pictures are quite different from pictures taken manu-
ally: full of action and often hilarious.
In the following sections, we will present some scripts from these areas.
All of them aim to be as independent of platform and camera model as
possible, but you should first test them with your own camera to see if they
are suitable. The main reason for presenting these scripts is so that you can
learn something about scripting. After playing with the scripts found here
or on http://chdk.wikia.com/wiki/
ate your own scripts and draw even more benefit from the CHDK.

5.7.1 Time machines

Why do you need a script shooting a series of photos? Doesn't your camera
have a configurable series function? Of course it has.
But you probably have noticed that this function has its limitations.
First, the number of shots is limited to 10. You may have an initial delay
before the series begins but no delay between pictures, and exposure and
focus are only measured once and not for each image. The latter can be a
problem if the series function allows for long series with customizable de-
lays. For example, during a long series, the illumination may change due to
the sunset or a cloud hiding the sun.
There are quite a few reasons to look at time-lapse scripts—and in fact,
most of the CHDK scripts available on the web are for time-lapse purposes.
We will present two scripts here. One simply takes a predefined number
of shots with a predefined delay between each shot. It does this very pre-
cisely, even taking different shutter and image processing times into ac-
count. So, it will even keep to the schedule when exposure times become
quite long. The other reads a predefined schedule from a text file and fires
the camera at precisely the defined points in time. Such schedules are most
useful for unmanned operations like balloon or kite photography, but they
need to be prepared on a PC because the schedule must be supplied as a
text file.
Both scripts are written in Lua because it is easier to get a precise timing
in that language. A third script (also written in Lua) deals only indirectly
with time series; it is used to rename images. That might be necessary for
some time-lapse moviemakers. Here we also have the opportunity to try
out Lua for file management.
UBASIC/Scripts, you may be able to cre-