1 ACCEPTED SOLUTION
If the camera was working properly, then started overexposing in auto mode, most likely you have changed some setting....
Go into the menu, select and use "Clear All Camera Settings". You also might want to go into the Custom Functions menu, select and use "Reset all Custom Functions".
As a last resort, you might do a "reboot" of the camera. This is a lot like rebooting a computer, to clear incorrect instructions that are stuck in the memory.
To do a reboot, first turn off the camera, then remove all the batteries including the little silver "memory battery" that's in a drawer inside the main battery compartment. Turn the camera on and press the shutter release button once. It won't fire without batteries, of course. But doing this drains all the residual power in the circuitry.
Turn the camera off, reinstall the batteries and turn it back on. Check the date/time. If you got a proper reboot, they should need to be reset.
If you didn't get a proper reboot, you also can go through the same procedure, but instead of pressing the shutter release button just leave the batteries out for about an hour. This should allow any residual power to drain off and cause a full reset, too.
All these can clear some setting you've inadvertently set, that's causing problems. Or it might clear some instruction string stuck in memory, much like rebooting a computer will clear it's memory and help it work better. (After all, digital cameras are essentially handheld computers. 
)
You also might consider reinstalling (upgrading, if needed) the camera's firmware. Sometimes it can become corrupted and give problems. If you go to the Canon website and search for 30D, under the Software and Downloads category you will find the latest version of software for the camera and instructions on how to install it. Follow the instructions carefully. It's not hard, but has to be done as instructed or there is some risk of "bricking" the camera.
Finally, it could be a mis-communication between the camera and lens. Some flashes use distance data from the lens to help set the strength of the flash output. Remove the lens and clean the contacts. Usually the best way to do this is to carefully wipe the gold contacts on the rear of the lens with a clean rag that's been slightly dampened with a few drops of isopropyl alcohol (cheap rubbing alcohol is fine). Just be careful to keep off the lens' optics and to not touch the mirror inside the front of the camera or the focus screen right above the mirror.
You also might check that the spring loaded "pins" corresponding to the contacts on the lens are working properly. Gently press on each pin and watch that it springs back into place. Sometimes these can be sticky, causing communication problems between the camera and lens.
Clearing the settings to factory defaults and/or rebooting the camera you will lose some other settings you've made and will need to go into the menu to manually redo any settings you regularly use.
All these are things you can do yourself and that cost nothing to try. They may or may not help. If so, great. If not, you'll need to have a repair tech look at the camera. Either find someone local who can work on it or send it in to Canon's Service Dept.
***********
Alan Myers
San Jose, Calif., USA
"Walk softly and carry a big lens."
GEAR: 5DII, 7D(x2), 50D(x3), some other cameras, various lenses & accessories
FLICKR & PRINTROOM
Does this tend to happen most often with photos taken really close to your subject?
Just as a flash has a limit on how far it can reach, it also can overexpose if used too close. If using an accessory flash, many of them display a distance scale on their LCD screen, showing distances that are both too far and too close, for any given aperture and ISO combination.
Rather than just using Program and adjusting Flash Exposure Compensation, you also can set the camera to Av (aperture prefered auto exposure) and use a smaller aperture. Reducing your ISO to a lower level can help, too.
You also can use some sort of diffuser over the flash itself, to reduce it's output. There are various products you can buy, but for macro work with standard flashes I often just put a couple layers of white gauze bandage over the flash tube, held in place with a rubber band. You can vary the amount of diffusion by adding or subtracting layers of the gauze bandage, as needed.
I used this arrangement to shoot the following image, which by rights was way, way too close for a standard flash and should have been completely blown out...
There are still other things you can do to "dial back" your flash's output.
If it's an accessory flash with a zooming head, make sure you are using the correctly set focal length.... Or if working exceptionally close, you could even manually override it and set it to wider than the focal length of your lens. This will spread the flash's light output more, reducing it's strength and reach. Some flashes even have a wide angle adapter or panel, too. If yours does, you might try using that to further reduce the flash output.
Or bounce the flash off a nearby wall or ceiling. Or, some flashes can be fitted with a bracket and white card to provide more portable bounced flash.
***********
Alan Myers
San Jose, Calif., USA
"Walk softly and carry a big lens."
GEAR: 5DII, 7D(x2), 50D(x3), some other cameras, various lenses & accessories
FLICKR & PRINTROOM
If the camera was working properly, then started overexposing in auto mode, most likely you have changed some setting....
Go into the menu, select and use "Clear All Camera Settings". You also might want to go into the Custom Functions menu, select and use "Reset all Custom Functions".
As a last resort, you might do a "reboot" of the camera. This is a lot like rebooting a computer, to clear incorrect instructions that are stuck in the memory.
To do a reboot, first turn off the camera, then remove all the batteries including the little silver "memory battery" that's in a drawer inside the main battery compartment. Turn the camera on and press the shutter release button once. It won't fire without batteries, of course. But doing this drains all the residual power in the circuitry.
Turn the camera off, reinstall the batteries and turn it back on. Check the date/time. If you got a proper reboot, they should need to be reset.
If you didn't get a proper reboot, you also can go through the same procedure, but instead of pressing the shutter release button just leave the batteries out for about an hour. This should allow any residual power to drain off and cause a full reset, too.
All these can clear some setting you've inadvertently set, that's causing problems. Or it might clear some instruction string stuck in memory, much like rebooting a computer will clear it's memory and help it work better. (After all, digital cameras are essentially handheld computers. )
You also might consider reinstalling (upgrading, if needed) the camera's firmware. Sometimes it can become corrupted and give problems. If you go to the Canon website and search for 30D, under the Software and Downloads category you will find the latest version of software for the camera and instructions on how to install it. Follow the instructions carefully. It's not hard, but has to be done as instructed or there is some risk of "bricking" the camera.
Finally, it could be a mis-communication between the camera and lens. Some flashes use distance data from the lens to help set the strength of the flash output. Remove the lens and clean the contacts. Usually the best way to do this is to carefully wipe the gold contacts on the rear of the lens with a clean rag that's been slightly dampened with a few drops of isopropyl alcohol (cheap rubbing alcohol is fine). Just be careful to keep off the lens' optics and to not touch the mirror inside the front of the camera or the focus screen right above the mirror.
You also might check that the spring loaded "pins" corresponding to the contacts on the lens are working properly. Gently press on each pin and watch that it springs back into place. Sometimes these can be sticky, causing communication problems between the camera and lens.
Clearing the settings to factory defaults and/or rebooting the camera you will lose some other settings you've made and will need to go into the menu to manually redo any settings you regularly use.
All these are things you can do yourself and that cost nothing to try. They may or may not help. If so, great. If not, you'll need to have a repair tech look at the camera. Either find someone local who can work on it or send it in to Canon's Service Dept.
***********
Alan Myers
San Jose, Calif., USA
"Walk softly and carry a big lens."
GEAR: 5DII, 7D(x2), 50D(x3), some other cameras, various lenses & accessories
FLICKR & PRINTROOM
