Canon Camera, Руководство хакера

Страница: 233 / 257

224
C H A P T E R 7 The Stereo Data Maker (SDM)
use the Custom timer with a few seconds delay to fire the camera (obvi-
ously not an option for action shots). Anything else will lead to shattered or
unsharp images.
After setting up your tripod and camera, you should carefully focus the
camera/scope combination. This is done with the help of the scope’s focus
control while looking at the camera display. For better control, you may want
to switch the camera’s screen magnifier on. In the native camera menu, set
the
AF Frame to Center and the AF-Point Zoom to On . Upon half-pressing
the shutter button, the center AF frame is enlarged—but only if this area is
sharp enough. So the
AF-Point Zoom can act as an in-focus indicator.
7.9 Scripting
Not all uBasic commands and not all CHDK commands are supported by
the SDM. For example, the SDM does not know the uBasic instruction
select (section 5.3.5) or the CHDK command get_display_mode (section
5.5.8).
On the other hand, the SDM introduces a large number of new com-
mands. Some of them are synonyms of existing CHDK commands. Their
only rationale is to make the script more readable. For the same reason, it
is also possible to omit the
print
command and simply write a string into
a script line. For example:
"Hello SDM!"
will output
Hello SDM!
on the camera’s display. Other commands simplify tasks that would need
elaborated scripts in the CHDK, especially in the areas of bracketing, time
lapsing, and communications. And, the SDM can do one thing that is not
(yet) possible in the CHDK at all: switching between photo and video mode.
The following is a small sample script that waits on a signal from the
USB port (from a remote control, an RC wireless, a microcontroller, etc.) and
then shoots a movie for the specified number of seconds:
@title Movie
@param t Duration(sec)
@default t 5
"Waiting on Remote"
wait_for_switch_press
"Shooting movie"
"Please stand by"
shoot_movie_for t
end