Strobes

Strobes

With both a D-SLR and a digital compact camera, a strobe is almost always a necessity. Choosing the right strobe for your system is vital to creating good photographs. These are a few things that you should think about when choosing a strobe for your digital underwater system.

Angle of Coverage

If you are shooting with a 20mm lens and the strobe can only illuminate a 28mm lens angle, then your photo will appear dark in some parts. A way around this is to add a diffuser. A diffuser is a piece of white plastic that is placed over the strobe that difuses the light out in order to cover a wider area. This works well, but it takes away some of the power of your strobe.

Power

Strobe power is another important factor in selecting your strobe. You do not want a strobe that is not powerful enough. You can tell how powerful a strobe is by the manufacturer’s guide number. A guide number tells the user the relative output of the strobe for comparisons with other strobes. Generally, guide numbers are between 15-52. Make sure that the guide number is an underwater guide number and not an above-water number. If only an above-water guide number is given, divide by three.

Size

Another thing to take into consideration is the size of the strobe. One that is too bulky might be powerful, but it can also be a hassle to travel with and may just wind up illuminating too much backscatter for good photos to be created.

Digital Compatibilities

Using a strobe with a digital camera is a very complicated situation. Before digital, film users could attach a strobe to their camera and use what is called TTL exposure. This ensured an almost perfect exposure all the time. But digital cameras use different technology to judge exposures, and different manufactures use different technology, thus creating a real problem for strobe manufactures. To correct the problem, many digital underwater photographers use strobes that have various power settings and, based on the shot, adjust them to what they think would be appropriate. My strobe, the Sea & Sea YS90, Auto has 12 power settings that let me adjust the amount of light coming out of it. After a few dives, it is pretty easy to guess which power setting to use for which shot. The good thing about digital is if you guess wrong, you can see it in the LCD screen, and adjust the settings and re-shoot; whereas with digital, you figure out what you did wrong only after you get the film developed.

There are always technical advances being made, and I am sure that eventually there will be systems that can use TTL techniques or better to obtain a nearly perfect exposure, but until then, using a strobe that has many different power settings is what digital underwater photographers have to do.