Originally posted by valhallasw The obvious difference between the ok and overexposed are the flash strength, but I cannot find why it is much stronger
I assume it has something to do with the Flash Metering Segments, but that still does not answer the question of why
Do you have the option set to allow you to shoot before the flash has fully recharged? And do you think it's possible that this is what happened on the underexposed shot? (BTW, it's also a different shutter speed and focal length than the other two).
Not sure what happened the overexposed shot, but I'd observe that setting ISO 1600 and shooting at point blank range like that is going to be tough for the flash system to control - it's going to have to hold back an awful lot, with little room for error. My guess is you'd get more consistent results at lower ISO settings.
I also wonder why you're using spot metering. That's pretty much *guaranteed* to give results that are all over the map unless you are very careful to point only at subjects that are exactly 18% gray in value. Without flash, spot metering can be useful in conjunction with the AE-L button to set an exposure off a neutral subject and then reframe and shoot, but you can't really do that in conjucntion with flash, since the flash metering will still be based on what you're pointing at when you hit the shutter.
So, my advice: make sure option to allow you to shoot while the flash is charging is turned off, lower ISO, and switch to a more sensible metering mode for the application (multisegment or center-weighted), and see if things don't improve.
BTW, the values under "Flash metering segments" seem very different, and I wonder about all those n/a's in the bad shots. But I don't know how to interpret these numbers.