Question about ETTL on T2i

I have a Question on how my Canon T2i meters for the exposure when in ETTL with a flash mounted.

First some info about my setup:
I have the camera setup for Back Button Focus / * Focus or whatever the true name for it is called.
I like this setup because i can push the * button to focus on the subject and then recompse the shot without having to keep holding any buttons down.

I also have the focus point set to only the center dot.

So I put the center dot on my subject, push the focus button to focus, recompose the shot so the subject is off center, say to the right of the frame.
An example would be taking a pic of my wife where she is in the right side of the frame about 6ft from me.
The center focus dot is now pointing at a wall that is 10ft behind her 16ft from me.

So my question is when i push the shutter button and the flash fires is the ETTL metering for her where i have focus
or is it metering for where the red dot is in the center of the frame, which is actually the wall 16ft from me?

I'm wondering because some of my shots seem overexposed when the subject is closer to me and the center dot is actually pointing at a much further distance when the shutter button is pushed.

Depends on what metering mode are you using. Evaluative, average of the whole scene. Spot - depends on when you locked it using the half-press of the shutter button and where the center point was aiming at.

To me, it seems like the camera is adjusting flash power for your background. Try using spot metering and lock it by half pressing the shutter button while your focus point is aimed at your wife.

If your subject is a small part of a large dark scene then the flash will tend to overexpose the subject when Using eTTL. You have to recognize when you need to dial in plus or minus FEC.

I think it's set to Evaluative, but I'm not sure and not near my camera right now.

Thanks for the tips! I always forget about the FEC option. I will have to play around with the settings.

Listen to him, not me. He knows what he's saying.

dedsen wrote in post #13778440
If your subject is a small part of a large dark scene then the flash will tend to overexpose the subject when Using eTTL. You have to recognize when you need to dial in plus or minus FEC.

In Evaluative mode, ETTL flash ordinarily uses the AF zone used for focus, and also factors in any other zones which are at the same distance as the AF zone.

How it behaves when AF point is centered and used via the rear focus button, but then reframed so that the subject is at a different AF point when the shutter is pressed and the ETTL pre-flash is read...I don't know. I presume that the center AF point (and similar distance zones) is used, so if those zones are significantly different in brightness than the subject, the flash could well be fooled. Worthy of conducting a controlled experiment to see how it behaves!

trossite wrote in post #13778293
I have a Question on how my Canon T2i meters for the exposure when in ETTL with a flash mounted.

This references the 1D Mark II, but it does explain where and how E-TTL II meters. The main differences (from the old E-TTL) are metering is no longer linked to the focusing point and distance information from the lens, when available, is used.

https://photography-on-the.net/forum/showthre​ad.php?t=46311

Great link oldvultureface, thanks for pointing me towards that!

trossite wrote in post #13778293
An example would be taking a pic of my wife where she is in the right side of the frame about 6ft from me.

If you're getting unsatisfactory or inconsistent results from E-TTL with a stationary subject at a fixed distance, press that mode button on your flash 'til the 'M' shows on the LCD and adjust the flash output manually. On the other hand, when conditions are constantly changing, E-TTL will at least get you in the ballpark.

I'm just and I mean just starting to venture into the manual mode of my flash. My dad was letting me borrow his Vivitar DF383 that he just uses as a spare off camera flash.

I just got the Yongnuo 565EX, which is a lot more powerful than the Vivitar. I haven't used it a whole lot yet and I think i'm just not used to how much brighter and powerful it seems over the Vivitar.