Here's how I lit the tank. There are a total of four flash units on these shots. Not counting the one on the camera (set to manual 1/128th power)...here is the set up of the other three. Two Nikon SB-900's on top...one SB-800 on the bottom.
I moved the gravel away from the bottom of the tank to light the bottom of the fish. In the past I would have to use a diffuser (Gary Fong to be exact) to cut the amount of light that was illuminating the bottom of the fish. This posed a few problems.
First it was difficult at times not to get a "hot spot" on the fish. It really was very dependent on how close the fish was to the bottom of the tank...and close to the flash. Ideally the fish should be equal distance (more or less) from all of the flash units. If not it was a matter of adjusting output through the camera's control center.
Second....because the diffuser would effectively "scatter" the light, I would invariably get some bleed over into the background of the tank. This was a tough one. I found a very nice and very inexpensive ($39) diffuser that does a great job. It is essentially a reflective sheet that attaches to the flash and allows you to "bend/fold/roll" the edges to fit your need. What I did was simply curve the back end so that it would cut the amount of light reflecting on the bottom.
I generally would put two flash units on top of the tank with diffusers. For this I switched out the normal diffuser that was more or less an inverted bell shape and replaced it with a Grsslon flash diffuser. If you take a look at this photo you can see how wide it is. The flash is pointed straight down through the diffuser. Inside the diffuser there are reflective light bellows that disperse and soften the light over a much wider area.
And finally I wanted to fill in the side of the fish with a soft light to cut the hard shadows. A big part of what I am doing relies on the set up....AND the participation of the fish. Basically I leave it up to the model to pick the pose. The reflective soft box flash unit did an exceptional job. The flash on the inside is on a rail and can be moved forward or back to give more or less light.
I am constantly tinkering with the light set up. All of my tanks are painted on the back with a "frosted glass" spray paint. It give them an opaque pebbled texture. Some of the tanks then get a flat black second coat. This combination does a great job preventing that reflective flair that sometimes comes from over spilling light.
I wanted to see what a little back light would look like and started by moving the umbrella toward the back of the tank and compensating for the front light by bumping up the output of the camera flash...and got this shot.
Full disclosure I got more "oops" ...pictures I will never post....here than most shoots. The key of course is to continue to experiment with your set up and don't settle for average. Through trial and error I got ONE shot that I thought was different...at least from what I normally post.
With the exception of the algae at the back bottom of the tank...something I never have to worry about showing up under normal circumstances...I liked the effect. It sort of resembled sunlight coming down.
The biggest challenge I had here....all of the light that I used forced the camera to almost "squint" through the lens. I had to shoot at the lowest ISO, the highest aperture and the fastest shutter speed (1/320th) in order to cut the light. In addition, most of the flash units were set to at least half to quarter power.
In the end...
...it's all about light, luck and practice. :D
