146 CHAPTER 5 Scripting
M3 W
Superfine 119 sec 48 sec
Medium 202 sec 78 sec
Low 406 sec 156 sec
When shooting at intervals of one minute, a 4 GB card can cover a mini-
mum of one day and a maximum of 8 days 11 hours. An external power
supply is highly recommended for such a task. Changing batteries during a
shooting session can easily ruin the whole set-up.
By the way, long time-lapse sessions can wear out your camera. A movie
with five minutes’ playtime at 30 fps consists of 9,000 single shots. The
fewer moving parts your camera has, the better. (Using a DSLR with its
complex mechanics and mechanical aperture is not a good idea.) A small
compact camera with an electronic shutter and a neutral density filter is
definitely preferred.
Also, be careful about the Digital Zoom. When shooting HD movies, you
should avoid the Digital Zoom altogether or only use it up to approximately
a factor of 2. Otherwise, you can use any camera feature and any CHDK
feature that you would use when shooting manually. You can allow the
camera to determine the exposure and focus for each new shot, or you can
use Overrides (section 4.3.1) to set fixed exposure values and/or a fixed
subject distance. You can use extreme exposure times (sections 4.3.5 and
4.3.6). You can even use curves (section 4.3.8) to compress contrast or do
some wild, experimental stuff. You can bracket every shot, later applying
tone mapping to each exposure group to create an HDR movie. There are,
in fact, some specialized scripts for that task in the community, and we will
discuss this technique in section 6.3.
After a time-lapse session, you will end up with a series of photos—not
with a video. Additional post-processing steps are required to convert the
photos into a movie:
f
First, some resampling might be required, depending on the selected
image size during shooting and the target output format. You will need
a tool that is able to downsize images in a batch process. There are a
number of tools for this purpose. If you have Photoshop, you can use
Actions. Similarly, in Paint Shop Pro you would use Scripts, and in Picture
Window you would use Workflow. Free tools with batch facilities in-
clude IrfanView, Picasa, and the command-line tool Image Magick. On
the Mac, you can create an Automator action.
f
Finally, you must feed the images into a time-lapse converter. Suitable
programs are Quicktime Pro, iMovie (Mac), MovieSalsa, MakeAVI (free),
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