I have the same problem with my 10D and canon flash. My suggestion, use manual and set the flash power to 1/4 or 1/2 and use the LCD to check your exposure. Don't shoot the flash at full 1/1 or you'll burn it out quick. Also, get a quantum turbo battery and adapter cable so you'll recycle quickly
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There are ways to adjust metering modes on your camera to work well with the flash, but I've found it better to just to leave it manual and adjust exposure according to the LCD.