[Leica] Fill Flash

["Johnny Deadman" <deadman@jukebox.demon.co.uk>]

Pardon me if this is old ground (if so, could someone post me some 
references?), but I have a question about flash/ambient ratios which I have
not seen covered, but always makes me think twice while shooting --
something I hate to do.

I use a Vivitar 283 off the camera with either a stofen softbox or one of
those strange parallelogram/silver paper affairs that velcros (TM) onto the
top of the 283. You know what I mean. All powered off a Quantum 1, as if
that mattered.

Shooting in daylight, I set the flash to auto and one stop wider than I'm
actually using on the camera...so if I'm shooting at 5.6 I set the flash to
f4 mode. This gives a 3:1 ambient:flash ratio.

The problems start when dusk falls. As the ambient light drips away, the
shutter speeds get longer and longer. Up to a point, I don't care if the
background goes wobbly: it's an over-used effect these days, but if you take
care to keep the camera as still as possible, it's still pleasing. Anything
longer than 1/4 sec is pointless affectation, however!

But here's the rub: as the ambient light falls at the violet hour and the
shutter speed increases, I am always torn about how to rebalance the
flash/ambient ratio. The problem is compounded by the fact that this is the
most wonderful time to shoot and lasts such a short time that worrying about
light balance is the last thing I want to do.

My head tells me that as soon as I am not confident about holding the camera
steady -- once I'm shooting at less than 1/30 -- I should REVERSE that ratio
so that I am now shooting 3:1 flash:ambient. So I usually leave the flash at
f4, say, set the camera to f4, and set the shutter speed one stop faster
than my light meter says I should.

Since I don't consider doing this until the shutter speed falls below 1/30,
I never end up with a shutter speed out of sync range.

The point is twofold:

1:    Avoid evenly balanced light sources...yuk!
2:    Make sure the sharp flash image dominates the blurry ambient image

However, my heart always tells me I should be making a more gradual
change...exposing for the ambient light as long as possible...letting the
balance change gradually instead of suddenly snapping over from one ratio to
the other.

I wonder if anyone else on the LUG has a strategy for dealing with this
situation, and what ratios people use for (1) regular daylight fill (2)
night shooting where the flash image is dominant? and (3) the $64k Q --
dusk, where you are on the cusp of (1) and (2)?
- --
Johnny Deadman

"The obscure man's reflections may be aw wise as the rich cheese-maker's, on
everything but cheese" - Haskins