Hi,
Assuming anything isn't really wrong with the camera ( I don't know) read below. It explains that the camera isn't under/over exposing just because the ticker on the meter is in the middle. It is programmed to read for 18% grey. If you already know everything below, and there is something going on with the camera that I don't understand I apologize. But maybe it can help someone understand the temporarily illusive concept of exposure. Once it clicks, its nice!
Whatever you meter, if you set the ticker to the middle your camera will make that grey in your picture. If you meter a white card and set it to the middle of the graph, then all of your whites will be grey and your pictures will be underexposed, assuming you took the camera to mean that was the correct exposure.
If you meter off of a jet black card and then take a picture of that it will be grey. All blacks will be grey and if you take that to heart, than all of your pictures will be over exposed.
If you meter of an exact grey card, that is lit properly, and evenly than that will be grey and you will have correct exposure. The trick to a greycard is that if uneven light is hitting it then it can be off. It is just truly a starting point because I feel that exposure, once at a certain level, is subjective to the look you are going for.
So if you meter for white, black, and grey and take a picture of each card the pictures will all look identical grey if you set the ticker to the middle.
All the camera meter does is assumes whatever you are metering is the 18% grey (they get that because most scenes will average out to 18% grey in reflected light). But you have to know if you are metering off of something lighter than grey, then your picture will be underexposed if you don't take it into consideration and go to the right on the meter graph. You have to keep trying new exposures until you get what you are after. Eventually it will be second nature.
If you are metering off of something that is darker than 18% grey, and you take it to heart and go with the middle ticker, than your picture will be over exposed. In this case you need to go to the left of the ticker.
Take a baby for instance. If you are taking a picture of a light baby on a light background the camera will give you settings for the ticker to be in the middle. What you were considering "correct exposure". In realty there is a ton more light coming off of the scene then would if it it were all grey. So the camera will suggest to you that you turn all of those whites and light colors grey and underexpose. You need to learn how to evaluate the scene and compensate for it being light be setting the exposure to what appears to be over compared to the camera ticker.
I hope this explains it a little. Do some experiments, take a white piece of paper and shoot it where the camera has the ticker in the middle. Do this with black and your grey card. You will see that they all will be grey. Then under and over expose each one until you get the true values. This should show you how the camera meter works better.
