Balanced light with "TTL" in WA shots, how does it work?

On a dive trip to Narvik last week I got the first chance to actually try to balance natural light with flash, something I'm not so spoiled with my usual black water diving.

I ended up using manual mode exclusively to get the amount of natural light i wanted, and then add manual flash, where i adjusted the flash power to get the effect i wanted.

My question is how do you use TTL in this situation? Is the camera able to "understand" that I want to get the weak background light to balance the flash.

The flash lit part is sometimes a construction detail or a diver in the foreground, not necessarily in the the center, but sometimes at the edges.

(Camera is Sea&Sea DX-G1 + YS110 strobe)

Cheers

/O

Even cameras with sophisticated metering algorithms struggle with this, so manual is the way to go.

In Nikon cameras the "matrix" metering is referred to a library of typical image compositions and gradations of illumination: these standard images are nothing like the typical underwater wide-angle image, so TTL metering gives peculiar results. In the tropics I find that my strobes won't fire at all, in the north that the strobes dramatically over-expose the foreground.

Tim

As a general rule for topside photography where EVERYONE but studio photographers use TTL - you set your flash meter at around -1.5 stops for fill flash.

The same probably holds true underwater - set your flashes to -1.5 or perhaps -1 for fill flash.

Cheers

James