Got this questions on Flash Syn Speed. I'm using F80 and it got a flash syn of 1/125. From my understanding, it means that when flash is use, the highest possible speed is 1/125. And any speed above that will have banding effect as the shutter curtain not fully open when flash is trigger. (correct me if I got it wrong)
1) Does this 1/125 only limit to the build-in flash and what X-contact only mean?
2) If use SB flash (eg sb50dx or sb28) can the shutter speed be faster than 1/125?
3) If uses bounce flash, do I need to reduce the speed of shutter slightly (slower then 1/125) or just use it at 1/125.
4) 1/125 seem kind of slow, is there anyway to increase the speed?
5) Just an example (not an actural case). In a bright sunny day, I wanted to shoot an a person outdoor, If I use a AP at f3.5 to throw the background out of focus, the meter required a shutter speed of say 1/500. But to remove the nasty shadow on the face, I use fill-in flash (build in). Hence the camera will reduce the speed will reduce to 1/125 (right?). In this case, will the picture be overexposed? I got a feeling that the person will be correctly expose but background will be overexpose. How can I achive a better picture if I want to maintain that kind of f3.5 DOF.
Thanks for any info input.