I just scored a 70mm lens for my Mamiya 645. It's the one with the leaf shutter, so the flash synchs at all speeds. My question is, what setting do I use on my Vivitar 285HV flash? Do I just use it as I normally would (estimating the distance, setting the flash on the red, blue, yellow setting etc.) Am I making this more complicated that I need to? Thanks in advance for any advice.