20D Overexposure Question

Started Jun 10, 2010 | Discussions thread
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GPapa
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20D Overexposure Question
Jun 10, 2010

I have a 20D with just shy of 130,000 shutter actuations. I had the camera serviced for a shutter button failure last fall at just a bit over 90,000 actuations.

This spring, during the first outdoor sports event, all of my images were over exposed when shooting in Aperture Priority mode. During winter/indoor sports events all of my shooting was done in manual mode, using the histogram to adjust exposure.

After some fiddling around resetting all of the settings in my camera I figured out that I could get reasonably well exposed images in AV mode by setting the exposure compensation to -2/3. I didn't have to do that last year so I'm thinking there is something off specification in the way my camera body is functioning.

I was at a public function chatting with a local photographer and mentioned the problem I am having. To my surprise he said he recently started having the same problem, in his studio, with a 20D, even though he uses manual exposure and an external light meter.

The one thing we had in common was that we had replaced the original batteries with new batteries. I pulled out the old battery and tried it with similar overexposure results.

Just the other day I was shooting an awards ceremony and mentioned to the woman next to me that I was having problems with the exposure settings in my camera. She said she was too. She said she had a Canon XTI and that the problem had just started recently.

I told her I thought we were having problems caused by the fact that we had just crossed the galactic plane and have entered a higher frequency universe.

Actually I suspect that my shutter mechanism is failing, which at 130,000 actuations should be expected. I suspect that it is not really closing as fast as the specs indicate. I get similar results using different lenses.

I have done multiple searches on the web and have not found any one else discussing similar problems other than some vague reference in one post related to shutter mechanism failure. I think it is really odd that if there are three folks experiencing the same issue in my small town that there are not a whole bunch of folks talking about it in camera forums.

I am including the photo below to illustrate. The image as posted was darkened using Digital Photo Professional software and it is still somewhat overexposed. Maybe some of you folks can help me out here. I am noting that the focus is accurately placed and the shutter speed is 1/5000. I'm thinking the ball should have been stopped. This is a high school softball game. If there is a 1/4 inch of movement on the ball then I calculate it must be traveling at about 70 miles per hour. That would be about 12 miles per hour faster than the very best college level girls softball pitchers.

I guess if my 1/4 inch estimate is an overstatement then the ball would be traveling at a slower speed, but that does not explain why all of my images are suddenly overexposed. Anybody got any ideas?

Full size image:
http://longfellows.smugmug.com/photos/817640294_wwuwa-O.jpg

Date Taken: 2010-03-18 17:48:27
Camera: Canon EOS 20D
Exposure Time: 0.0002s (1/5000)
Aperture: f/3.5
ISO: 800
Focal Length: 90mm (144mm in 35mm)
Date Modified: 2010-03-18 17:48:27
Photo Dimensions: 2150 x 1536
File Size: 2.28 MB
Flash: flash did not fire, compulsory flash mode
Exposure Bias: 0 EV
Exposure Mode: auto
White Balance: auto
Color Space: sRGB

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