This tested the Ikelite DS125 with the Canon S40. I am photographing
the Ikelite strobe with the Canon camera. Thus I can visually tell if the
camera and the strobe are in sync, and can roughly compare the light
output of the strobe. The settings on the strobe were:
strobe off, on with TTL, and on at the various manual settings.
At the manual settings, the preflash on the camera triggered the strobe TWICE.
It was amazing thaat the Ikelite could still cycle in the millisecond interval
between the preflash and the main flash. However it was only able to do this
at the 1/8 and 1/4 power settings.
Conclusion: The Ikelite was not a good match for the Canon S40.