This sounds like it might be a defective CCD imager. If so, Canon should fix this for you for free, including free shipping both ways. This is regardless of your camera's warranty status. Please check the following two links for more info:
how to replace shuter button on A70. I dropped my camera and the button fell off. I bought a used...
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how to replace shuter button on A70. I dropped my camera and the button fell off. I bought a used broken camera the same model and I want to put the shutter on mine.
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