I see! From your earlier post I'd envisioned a dimly lit cavernous hall. I didn't realize you were working in an outdoor pavillion.
Oh Yes!! lucky me
As you know, you'll need to be pretty fast on your feet adjusting to the changing conditions. When the ambient light is bright, low ISO's, a fast shutter speed and (normally) very small lens apertures will be required to keep the ambient light under control but as the sun sets you'll need to be adjusting things towards the opposite end of the spectrum (dark cavernous hall mode).
Oh believe me I know!! I have been there to practice several times.
The main thing, whether shooting in bright sun, or night time darkness is to set your exposures to best take advantage of the available light conditions, whatever they are at the time. Your flash will then supplement that as needed, to help tone down the contrast, mainly by filling in the shadows.
Shutter speed will be the primary modulator of the ambient light. Aperture will mainly determine the output requirements of the flash. ISO more or less splits the difference.
Yes I know what you are saying. I don't have a problem holding either camera in horizontal mode, but portrait mode is more diffulcult for me. What I'm doing is resting the camera combos on my shoulder for stability. Standing at like a fighters stance to balance better. I did watch the video that several people linked me to, which is good advice, but he has the camera balanced on his clavical bone well I tried that several times and the camera doesn't come up to my eye. I can't afford a blurry picture or ghosting.
The bright light conditions will be the trickyest as they'll typically require more output from your flash than dark conditions as the flash will be competing with the sunlight. Normal sync speeds would typically require you to stop the lens aperture down about as far as you can to prevent blowing out the sky (or that mirrored floor!).
You can take advantage of the cameras high speed sync feature to help. That will also require some extra effort from your flash, making it less practical for use with distant subjects but as long as your working within 15 feet or so, it will allow you to use shutter speeds up to 1/1500s or so which will return the option of using wider lens apertures.
I will try that. It has to be that polished concrete floor because as I mentioned I can stop down to a f11 or even a f8 at the pavilion and they are silhouettes. At home I'm stopping down to a f11 and a f8 at the same time they would be walking down the isle and the exposure is perfect. If I'm working with high speed sync I'm thinking I will I will still get silhouettes though, oh but you said a wider lens aperture to compensate. I will try it. At this point as long as I get her exposed correctly I don't care if I blow the sky. I will fix this in PS by combining two exposures together if all fails.
With the flash mounted at the cameras hotshoe, the flash units TTL/BL (Balanced Fill) mode can help to automate problems with balancing flash on subjects that are placed in front of brighter backgrounds, though handling the problem manually will generally give you an additional level of control. A lot depends on your comfort level, but consider giving balanced fill mode a try to see how it works for you.
I have tried both. I think TTL/BL maybe working better.
For all the problems you'll have to confront, there will be that period just after the sun sets but before the sky darkens completely that you'll likely have some very nice ambient conditions to work under. Take as much advantage of that period as you can. Up until then, pray for some cloud cover!