Flash

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mushy

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I have a Canon 500D and a Canon Speedlite 430EX II Flashgun

When I set the flash and camera to auto; and am in a darkish room, the camera chooses an ISO of 1600 despite having the flash going off. I have tried switching the camera to AV mode and manually moving the ISO down to 200 and the pictures are still fine (because of the flash)

I thought the flash would talk to the camera in auto mode and alter the ISO setting to the light provided by the flash?

Is my assumption incorrect or am I doing something wrong? Is there a rule of thumb wrt what ISO setting to use when you have a flash?

Thanks
 
In auto (is that green square on Canon?) I expect it's following a settings within itself to get the shot regardless, so it's automatically upping the ISO to make sure there's no blur, camera shake or other movement.
 
See what happens in 'P' mode
 
The camera is trying to balance the ambient light exposure with the flash. It does this, in different ways and to different degrees, according to which mode you're in and any custom functions you might have set.

P is a fairly safe option. It will try to drop the shutter speed to balance the ambient, but won't go lower than 1/60sec. This setting takes the view that it is better to let the background go darker than risk any movement bluring.

Also check the custom function options in Av.
 
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