Canon Camera Hackers Manual page 187

178
C H A P T E R 5
Despite its tattered wings, this bee is
still busy collecting honey from a
borage blossom. Photographed with
the Macro Motion Detection program.
Canon Digital Elph SD1100 IS, 38 mm
(35mm equiv.), f/2.8, 1/430 sec, ISO 73.
Shot in DNG format, developed with
RawTherapee, somewhat cropped.
Scripting
Figure 5-5
Hat
The last scene program, > Hat<, is not actually used to capture motion. In-
stead, it's used to capture unaware people. The camera is placed some-
where, the script is started, and a hat is placed over the camera to hide it.
When something interesting happens, we lift the hat and the camera fires.
For this program, a simple 1x1 grid with a rather high threshold is fully
sufficient. Of course, focusing must be performed immediately before the
shot. We have also specified a high delay between motion detection and
the actual shot to allow for the hat to be removed completely. There is a
pause (normally five seconds) after the shot to allow the hat to be replaced.
The script begins with that pause, so after starting the script you have time
to cover the camera. In most cases, the camera should be set to autofocus
and automatic exposure.
Benchmark
The big question is, how fast is motion detection? This depends on several
factors: the camera, the script language used, and how well the script is
tuned. One keen CHDK user has provided the community with an aid for
determining the reaction time of motion detection scripts and cameras.
Just open the URL
browser and maximize the browser so that it fills the whole screen. Click
the Execute link. This will start a script that quickly fills a sequence of table
cells with black. After a while, the cells are made visible again and the cycle
is repeated.
http://dataghost.com/chdk/md_meter.html in your web