The Strobe Story - Shots in the Dark
In today's digital age, a powerful underwater flash has become more important than ever. Many popular digital cameras have squeezed even more pixels onto their CCD sensors, resulting in smaller pixels. This is not so bad on land in bright light, but in the darker light underwater the smaller pixels absorb even less light, making an external flash more important.
Many land digital cameras use longer exposure times when in low-light conditions or underwater. Unless the diver has an extremely steady hand and the sea creatures are completely still, blurred images may result. A strobe, freezing the subject for the split second the lens is open, solves this problem and helps to produce a sharp image.
The answer, then, seems to be to get yourself an underwater strobe. However, this presents a new problem, pre-flash. The external strobe is usually triggered by the built-in flash: When the built-in flash fires, it emits several flashes while communicating the light conditions with the camera, sometimes causing premature firing. When the camera lens finally opens, there is no more external flash. The result: a black picture.
First, if you can, lose the land camera with the underwater housing. Instead, get a dedicated underwater camera with a compatible underwater flash. You can't go wrong with these three brands to choose from: SeaLife, Sea&Sea and Botanica.
If you want to stick with a land digital camera, purchase one that allows you to manually control and shut off the pre-flash. With this option you can be more flexible with your flash purchase.
Another option is to experiment. You can start by reducing the camera's ISO speed to 100. The ISO speed controls the CCD light sensitivity much like film -- a slower ISO value results in sharper pictures in bright light conditions. You can also reduce the EV (exposure value) setting on your camera. The lower the EV, the less over-flash and more color your picture will reflect. If you are comfortable with manual settings, try selecting your own aperture and shutter speed to get the desired affect, experiment with output adjustments of the digital flash, or use a flash diffuser to soften the flash brightness.
Since they don't have great latitude or dynamic range between dark and bright extremes, digital cameras often want even and well-balanced light. For best results, try two strobes, mounted left and right of your camera.
If a new purchase is in your future, shop around. Some of the new strobes on the market are compatible with all camera models, from film to advanced digital. Some cameras, such as the ones made by SeaLife, also feature a flash control button for far, normal and close-up, plus exposure modes for land, underwater and external strobe. No matter what you decide, make sure you understand your camera's needs so you don't end up with shots in the dark.
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