Exposure/Lighting/

when I am doing in camera metering, and have my S. light attached. How much of a stop/many stops do I calculate in for my flash? i have a 580EXII and shoot with the xti.

Whats up with the big font? If you have the speed light in ttl mode you really wouldn't have to do anything from my understanding. The ttl mode acts as a fill flash. I guess it would be + or - for your liking.

That is a pretty loaded question. It all depends on what you are trying to do. The in-camera meter has nothing to do with what the flash is going to do. The camera meters for the flash in ETTL based on the pre-flash emitted by the flash. It will not register in your camera's displayed meter, it does it all internally and automatically.

Now, what I tend to do if using the flash as my main light source is to put the camera in manual and set it about 2 stops below ambient. I then set my flash comp to +1 to +2 (when bouncing). This will eliminate any ghosting from matched camera/flash exposures.

If using the flash as fill, I set the camera to a proper exposure, and the flash usually between -1 and -3. I only use as fill if my SS will be sufficient to avoid any motion blur.

Different situations must be treated differently.

Here is an amazing resource on flash photography:
http://planetneil.com …h-photography-techniques/