Latitude of Bounce Flash as Fill

We had a going-away party for one of our coworkers at a restaurant/bar with a wharf warehouse theme.  Weathered lumber was all over the place, along with barrels, crates and fishing nets.  It's how I imagine it would feel like being in an 18th century galleon.

Taking photos at this location was quite a challenge.  First, with dark wood everywhere and very high ceilings, there was no obvious place from which to bounce a flash.  Second, the dynamic range was quite high.  Most of the bar was kind of dark.  On the other hand, near the windows and under the lights, it was pretty bright.  Third, compounding the dynamic range issue, our group was having the party immediately beside the windows.  When balancing flash and ambient, having a dimly-lit subject against a bright background gives you a number of options.  In this case, when the subject is significantly brighter than the background, balancing flash and ambient is a little tricky.  Did I mention this place was dark?

We actually had a party at this same location last year.  At that time, I first tried using direct on-camera flash as fill and I didn't like how it looked.

Although the flash helped to reduce the dynamic range and illuminated the subjects while allowing the outside scenery to be visible, it did not look right (mainly because the light was coming from a direction that is different from where we would expect it to come from).  I gave up the flash and just went with ambient light only.

It certainly looked more natural, but the shadows were very dark, giving the images a very contrasty kind of look.  Nothing wrong with that per se, but it's not the kind of photo with mass appeal shall we say.

My primary objective this time was to improve from last year's shots by adding fill light, in a way that would complement the image.  I decided I would try bounce flash anyway, notwithstanding the less-than-ideal bouncing conditions.

It worked reasonably well.  I learned that conditions that would be impossible or difficult to use for bounce flash when using bounce as key can be feasible when using bounce flash as fill:

1. Power.  As a fill light, I'm using flash at -2 FEC or thereabouts.  Thus, using even a low ISO is possible (when bounce flash usually requires a higher ISO).  In these shots, I was using ISO 400.  That would be asking a lot from the flash in this kind of location if flash were the key light.  As the fill light though, I'm asking for only around 1/4th the amount of power I would otherwise require.  The power needed would be akin to shooting at ISO 1600 at 0 FEC, which is pretty realistic.

Bouncing from high ceilings at ISO 400

2. Bounce Direction.  As a key light, the direction that we're bouncing from is critical to the resulting image because it will determine the appearance of the shadows (and highlights).  When using bounce flash as fill, the amount of light the flash is contributing to the image is much dimmer, therefore the shadows that bounce flash produces are less noticeable (that's the whole point of fill light - you don't want fill light to cast its own shadows).  Bounce directions that I would normally avoid as unflattering may be usable when I'm using bounce flash as fill.

Bouncing straight up is usually not ideal but when it's only fill light, it looks ok.

3. Color.  Usually, I'm cautious about bouncing from non-neutral surfaces, like the dark wood at this location.  Once again, when bounce is only acting as fill, the color cast is less objectionable.

This is going to help me recognize bounce flash possibilities in seemingly impossible bounce conditions.