My camera is IXUS 850 and I have followed all the instructions,
all default values, set the Interval as 1 second.
I run the script for two times, indoor with medium lighting.
Both times turned out the scripts took photos roughly every 3 seconds.
The spec on that camera for continuous shooting is 1.7 pictures per second. That's without measuring brightness or changing exposure between shots. I've been experimenting with just metering brightness without taking a picture, and that takes 1.3 seconds. That adds up to 3 seconds per picture, which is the best you can do.
If you want to take pictures as fast as you can using the exposure measurement from the first picture, put your camera in continuous drive mode, where you hold down the shutter and it takes multiple pictures until you let it up. Than, you can run this script to hold the shutter down for you:
press("shoot_full")
while(true)do sleep(1000) end
