what would be a good portable/compact flash that works well with the medium format rangefinder camera Fujifilm GF670 (aka. Voigländer Bessa III)?
The main use case will be street photography, so it should be not too obtrusive (i.e. big) but it should also not be to weak. It should be a good compomise between the two.
It would also be nice if it had built-in light metering so I can should in automatic mode.
I use the Nikon SB 30 on the GF670 with pretty good results. It's small and has an automatic mode with 4 settings and an additional +/- 1/2 stop switch. Not sure if it's powerful enough for your needs but it's definitely small and portable.
Yes the Metz 20 c-2 works too. I was debating between the Metz and Nikon for the GF670 a few years back and ended up with both. I definitely prefer the Nikon over the Metz. The Nikon has more aperture settings in automatic mode along with the +/- 0.5 stop switch making it much more versatile. The Metz does have bounce but it's not powerful enough to really be useful. In my own (very limited) tests, I found the Nikon automatic mode to be more accurate too. Not to say the Metz is bad, the Nikon just seems to have it edged out.
I use the Nikon SB 30 on the GF670 with pretty good results. It's small and has an automatic mode with 4 settings and an additional +/- 1/2 stop switch. Not sure if it's powerful enough for your needs but it's definitely small and portable.
I use this too with a Mamiya 7. Awesome little flash and even has a slave sensor. Fun to use with a point and shoot which has its own flash to add some fill.
It's hard to go wrong with a vintage unit like a Vivitar 283. It was a mainstay for press corps photographers for many years. Has a couple of auto-range modes, plus manual. Guide number is 120 (ISO 100 in feet), as I recall. Plus it has bounce, which is nice for a more diffused look.