Av and Tv modes - light meter question

[yerp30]

ok...

Running into some exposure issues. The meter for fill flash or "light meter" goes from -2 to +2. 0 being perfect amount (i read that somewhere). In manual mode depending on how i set the shutter and aperture, the meter will automatically move depending on how much light comes in... over or under exposed... I dont have to set this. It will just automatically move itself on the meter and when it hits 0 it will tell me the shot is going to be perfectly exposed. In AV or TV it doesnt automatically move to tell me if its set to -2, 0, +2 or not.

Question is how come the meter doesn't move in these 2 modes and should I be messing with this? In order for some pictures to have the correct exposure I've been setting this depending on the lighting in these 2 modes. According to the histogram... this is how I am gauging if I am set correctly.

Any help is greatly appreciated.

Thanks ALL!

[savona]

Ok here is whats happening...

When you select AV mode its called Aperture priority. You select an aperture and the camera will automatically select a shutter speed that will give you a proper exposure, putting the light meter directly in the center (proper exposure). as you move the aperture up or down one step, the camera moves the shutter speed one step the opposite way to keep the exposure good, therefore keeping the light meter in the center.

TV mode is called Shutter Priority, it works the same way but instead of selecting an aperture you select the shutter speed. Then the camera will select the best aperture to create the best exposure.

These are referred to as Creative Modes.

M Mode is Full Manual, meaning you select ALL the settings and the camera doesnt make any adjustments. So when you change your aperture or shutter speed the camera is not making any adjustments and thats why your light meter move to under or over exposed.

Does that make sense and answer your question? Feel free to ask for further explaination. If you are not familiar with some of these terms look at the Glossary of Photography Terms here:

http://focusfaction.com/forums/faq.php?faq=terms

[yerp30]

It does answer most but here's the problem... Let's say I select Av mode and use F2.8 and I am in a room where there is soft lighting... The light meter doesn't tell me if the shot will be perfectly exposed. I took a shot for a test and the histogram said it was under exposed. So I raised the light meter to 1 and took the shot again. This time the shot being exposed correctly and the histogram indicating such. Why would I have to manually change the light meter to accomplish this if Av or Tv mode is supposed to do this for me?

[savona]

Well there could be a lot of things, for one there is a metering system between you and the subject. A metering system is what the camera uses to "meter" the light or measure the light hitting the sensor.

There are a couple different metering modes on most newer cameras. Spot metering which only exposes correctly for the center portion of the frame, evaluative metering which collects data from the whole frame and exposes best it can for everything. And center weighted metering mode which uses mostly the center of the frame but also takes in the rest of the frame for another fraction of the data. of course this is a very loose or broad overview of how these systems work.

So lets say your in a dimly lit room but you have a bright yellow subject (girl with a bright yellow shirt for instance). If you were using spot metering and metered for her shirt chances are the rest of the room would come out really dark since the camera only metered for the light bouncing of her shirt.

Its gets trick to use all these things to your advantage, but understanding them is the first step and your asking all the right questions! I hope this helps.