I have an Ixus 500 and my dad has an Ixus 700 (different names in the US I know, but they are compact digital cameras).

Last night I tried using an external flash to improve on indoor shots to try to get less 'harsh' photos and less red-eye. The flash has a sensor on it that detects the cameras flash and then it fires but the results were strange.

What resulted was an image that looked like no flash was used at all. Why would this be? Is the camera getting confused? I tried different angles and positioned the flash infront and behind the camera but still the problem is there. Theres nothing in the manual about it either.

Canon do sell an external flash for these cameras so I don't see why what I'm doing doesn't work. Does the Canon one perhaps plug into the camera?

Any help would be appreciated!

I used one of those external flash units for my ixus, and it did work, but it was tricky to get working correctly. It had a switch on the camera to adjust its sensitivity to the camera's flash. For instance, if I was using the ixus' red-eye mode, I needed to set the switch on the external flash unit accordingly.

The problem isn't likely that the ixus is getting confused, it's more likely that the external flash unit is getting confused and is firing at the wrong time. Re-read the unit's manual and see if there's anything about its settings, or the settings on the ixus, that will improve its operation.

Perhaps the camera is doing a quick pre-flash to measure exposure, white balance etc before the main flash. It it were then your external flash would probably trigger on the pre-flash.

I've noticed that some cameras will do multiple flashes (I assume to help with both redeye and closedeye). Maybe your cameras is set up to do that and the external flash is cueing off of the precursor flashes and flashing too early?

I thought about that but both cameras are only flashing once. The thing is though that the photos are as if there has been no flash used at all

By the way, here is the thread I started that resulted in me getting one of those external flash units.

Most if not all digital cameras these days use a preflash of some sort. It's extremely quick, and most people won't notice. They do this to evaluate the exposure of the scene, so as to be able to expose it properly. This means that a cheap external flash is never going to be able to just Do The Right Thing without commuinicating with the camera.

With an external flash which can ignore the preflash, you're going to have to put the camera in full manual mode, and then either use a light meeter or use trial and error to get the proper flash exposure. Not great for candids, but if you're staying in one place it's doable.

To really improve indoor shots you're going to want to get some sort of bounce option so that the light isn't coming directly from the camera for that "deer in the headlights" look.

Matthew