Great, it works on my SD980 too.
I was testing it with a fluorescent lamp, but I guess that's not a very reliable way, because the light depends on the voltage which fluctuates 50 times a second. I guess I should use an LED.
Did the SD980 have this problem as well?
Testing with flourescent or incandescent lamps should be OK in the general sense even though the voltage (and brightness) technically fluctuates, however they tend not to be "instant" on/off. You should still be able to see a positive exposure difference at least with a couple test runs. You should at least be able to 'see' a difference, I just wouldn't rely on comparing actual exposure values calculated from an image (i.e. trust the presence of an exposure change, but not the magnitude).
LEDs would be good if they are bright enough and DC driven. AC driven LEDs and arrays have an even worse flicker effect than incandescent or flourescent as they are virtually "instant" on/off.
[rant]
As a side note I really hate those LED chrismas lights and new LED brake lights you are seeing everywhere, as I can't detect the flicker espescially when in the peripheral vision range. They need to find a cheap way make them continuous driven (ie 3-phase or maybe a bias flow) In the very least they could alternate LED phases within the array, but I suppose this would require 2 circuits rather than just one.
[/rant]
