AE failure - meter degradation?

[reefhugger]

My D100 seems to not be getting auto exposures correct anymore, which is a recent development. I don't know if I'm imagining it, consistently shooting in low light situations without being aware, but it seems WAY off. Is this common for old digital cameras? I know people talk about the degradation of the sensor, can this happen to the light meter also? Thanks in advance for any help!

 

[Hertz van Rental]

Light meters in electronic and most digital cameras use photodiodes or phototransistors which, to the best of my knowledge, don't degrade.
One cause of your problem could be a software problem - digital cameras have built in software (called 'firmware').
Go to the manufacturer's website and make sure you have the latest version. Update if you haven't.
If that doesn't sort it then check the camera reading against a known light meter to see if there are any discrepancies. Do it in a range of light levels.
If the camera meter is off then it could be dirt on the light sensor or the circuit could be out of calibration (both extremely rare).
But if the meter is out you will need to take it to be repaired.

 

[reefhugger]

thank you, that was extremely helpful!

 

[Garbz]

Second on getting it repaired but it's incorrect to say the light is done by photodiodes. This was the case before the age of digitals.

These days digital SLRs and film SLRs too use a separate CCD sensor. In the case of the D200 it was 500pixels or so to form a light map of what the camera sees. It's part of every matrix / evaluative metering system.

Try a controlled shot. Shoot at a white piece of paper in spot or average metering modes and see if it comes out a neutral 50% grey.

 

[Hertz van Rental]

Second on getting it repaired but it's incorrect to say the light is done by photodiodes.

I didn't say all

Some digitals don't use a separate CCD but use the same sensor to both meter and record. It all boils down to who made it, when and how cheaply.
Whatever, it could still be a firmware issue so the first step should be to make sure you have the latest version and upgrade if not.
And contact the manufacturer - it could be a known issue.