How do you use supplemental flash for tank photographs? I would have expected serious problems with light reflection from the tank walls. Holding the flash at an angle might minimize that issue but wouldn't you have trouble getting the right exposure? I'd be interested in learning about the technique you used. Thanks.
The flashes I use are fairly specialized for macro photography. They have mount points way out on the end of my lenses because in macro shots, you are often so close to the subject that the shadow cast by the lens can cover the subject. But they are adjustable so that I can point them where I need them, so I can point them so that they won't make a glare on the glass.
But, the point of getting an off camera flash is that it's far more powerful and it offers you much more flexibility with regard to where you aim the light. As Nick says, it's about moving the flash so that it doesn't create a glare in the part of the glass you are shooting.
With through-the-lens photo metering and camera-flash communication, you really have a lot of control. Your camera can turn off the flash once you've gotten enough light for the exposure. I have a crazy theory about flash exposure control, though. I believe that the computer inside the camera wants to force the flash to play a fill-flash role. That is, the camera is trying everything it can to meter for the ambient light, only using the flash in a support role and never trying to use a flash as the main light for a shot where it can help it. I think it has a lot to do with engineer pre-conceptions about using as little power as possible so people don't have to constantly change the batteries.
That works fine outdoors in the sunlight, but aquarium photography is very low light and fish are very fast subjects. So, this means that the camera is constantly trying to use a very wide aperture and a very slow exposure speed and my fish photos without flash look horrible.
But, I'm taking most aquarium shots at home and I can essentially plug the camera into the wall if want to. (I use a supplemental, rechargeable battery pack.) So, I don't care how much battery I use with each shot. So, I force the camera to use a lot of power with each flash.
In manual mode, I purposely set the aperture to some very small number and I set the exposure to as fast a speed as I can, despite the fact that the camera's meter tells me that I'll be horribly underexposed. Then I take a test shot. The camera has no other option but to increase the power to the flash(es) and use them as the main light for the scene. The camera won't overexpose the shot. If it gets too much light, it'll cut power to the flash. If the test shot comes out too underexposed, I make adjustments to the settings and try again.
That's my flash philosophy. Like I said above, it doesn't work so well with some corals (acros look horrible with flash as the main light), but it works great with fish.
), I'm wondering how you would set-up to take a tank shot with off-camera flash so that you don't get reflections and get proper exposure. I've gone away from flash for tank photos for these reasons.
