On 2 ene, 19:34, (Adrian
Tuddenham) wrote:
I have a three year old Canon A420 which has been working perfectly
until last week. *Now pictures are coming out grossly over-exposed,
although they look satisfactory on the LCD screen right up to the point
where the release button is pressed. *

Moving from light to dark subjects, the system adjusts the image on the
screen to the changes in light level in a normal manner. *Holding the
release button half way down 'freezes' a satisfactory picture, but then,
after pressing it the rest of the way, the stored result is whited-out.

By deliberately choosing dark subject matter or something which needs
flash, I can force the correct exposure. *The picture then appears to
have a fine horizontal line structure imposed on it.

Given all your described sympthoms I would say it is the CCD sensor
starting to fail. It is showing some dark rows across the pictures,
typical of problems with these sensors. These dark rows make the
camera think the picture is darker than it is and increases exposure
to compensate. When you see the picture on its LCD live it is not
analyzing all the rows but a small fraction and these failing rows
have no impact at all, so it appears to work properly. But when you
take the photo it processes all the information.

I think the sensor will have to be replaced (if worth) but meanwhile
you can lower the exposure manually as you did as a workaround.
Consider also that overexposed photos may be corrected to some degree
with an editing program that can correct brightness/contrast. I get
quite good results with MS Office photo editor, my camera has a
tendency to take pictures too dark mainly under artificial light and I
fix some of them before printing.

Sorry if it sounds like bad news.