Quote Originally Posted by John Koehrer View Post
This is quick and easy. No fiddling around and it works the majority of the time. If you try it you may not bother with the other methods. But if you're trying to work in a set piece situation you WILL need to work a more accurate method.
I believe the Pentax 67 has a sync speed of 1/30 of a second so any comment regarding ignoring shutter speed should be taken with a grain(or two) of salt. Using a higher shutter speed will fire the flash before the shutter opens.
Unless you're using one of their leaf shutter lenses.
The 1/30 sync speed is not great, but not too big a challenge in the situation the OP described with an ambient of EV7.

As described that situation indicates an EI of 3200, if I did the math right.

What we don't know is how fancy the OPs flash unit is.

If it has an automatic mode like Nikon's "A" mode, the flash may be able to adjust its exposure to match the EI and aperture with no extra work.

If its a studio strobe it can be adjusted to exactly what is needed and tested with the flash meter.

If its an old flash unit, moving it closer or farther from the subject may be the only choice.