Underexposed 10d with speedlite

I have a 10D with a 550Ex speedlite.
When I shoot in fully automatic mode at a dark image, the result is underexposed.
I assumed that the camera and flash would automatically expose the picture correctly.
I assumed this because of the cost of the flash.
Am I wrong or is something broke, lighter images are not underexposed.
Any advice would be welcome

Could you post an example? My 10D with 550EX almost never underexposes. If anything it overexposes. I usually drop the flash power 2/3 of a stop to avoid the bright "blasted by flash" look. Generally, even a 220EX is more than enough flash for my 10D or Digital Rebel. Here's one shot at -2/3 stop on the 220EX flash, at ISO 200, Av mode 1/200 @ f/8. Good exposure on the dancers.

But Steve, they are shooting in Auto Mode, which makes a big difference doesn't it.

Your example is in Av mode where you set up a choice and the camera takes care of the rest.

What is wrong with the girl black top, blue jeans, there is a redness/bump just right of here belly button, very distracting.

Quote:

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Originally Posted by Flashram_Peter_AUS

But Steve, they are shooting in Auto Mode, which makes a big difference doesn't it.

Your example is in Av mode where you set up a choice and the camera takes care of the rest.

What is wrong with the girl black top, blue jeans, there is a redness/bump just right of here belly button, very distracting.

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True enough. Auto mode is a different animal. I never use it though, prefering either program mode with -2/3 stop flash exposure compensation (I have the software hack on my Rebel, so I have FEC enabled on my Rebel!). Or, as in this shot, because I wanted to freeze the action, I used 1/200 of a sec @ f/8 at ISO 200. The camera was a rebel, the flash a 220EX and the lens was the 18-55 kit lens.

The redness/blotch is either a tattoo or a birthmark. Whatever it is, it isn't the camera's fault. The mark is on her skin. Here you can see it a bit more clearly. Looks like a tattoo of a salamander.