For someone looking to purchase an underwater strobe for the first time there are so many features and specifications to choose from, that often, the first time photographer is deterred from purchasing an external strobe kit simply out of fear of selecting the wrong one. This guide will help you understand what the common strobe specifications listed by manufacturers actually mean which should help you in your decision making process.
If you missed the first part of this underwater photography guide click here.
featured above: Intova ISS 2000 Strobe Head available at Leisurepro.com
Cycle Time
Cycle time refers to the time it takes your strobe to fully recharge after firing to allow you to take your second shot. Strobes normally store the battery power in a capacitor that allows a large amount of power to send to the bulb when fired. Cycle time refers to the time needed to re-top up or recycle the capacitor drawing power from the battery. So the rule is, Faster is better. A 1 second cycle time is considered very good as you can take several consecutive strobe shots in quick succession; 3 seconds is a little slow, and beyond 5-8 seconds will prevent the photographer from getting good burst shots of moving subjects like fish, as you will have just one opportunity to get your photo perfect before it swims away from you.
Rated Depth
Rated depth refers to the maximum operating depth and corresponding pressure that the o-rings/ water sealing will withstand. The only consideration to keep in mind here when buying a strobe is to ensure that your strobes depth rating is equal to or greater than your camera housings so that you don’t accidentally flood the strobe following the cameras operating depth. However this is irrelevant for recreational divers, if your housing and strobe’s depth rating exceeds the maximum depth limits for recreational diving.
Featured above is the Sea & Sea YS-17 TTL Slave Strobe available at Leisurepro.com
Pre-Flash
Many underwater digital camera’s fire a pre-flash (or multiple pre-flashes), which is measured by the camera’s senor, and used to calculate exposure before actually firing the main flash that corresponds with the shutter opening. These Pre-flashes happens so quickly that the eye notices only one flash. So how is this concern? Well if you are not using a flash-sync cable, the external strobe usually fires when it senses that the onboard flash has fired. And since most digital cameras fire a pre-flash, this causes the slave strobe to fire before the shutter is actually open, ruining your images.
The Pre-Flash setting on your external strobe allows you to set your strobe to detect your camera’s pre-flashes and fire at the right one. So if number of pre-flashes is set to four, your external strobe will ignore the first three pre-flashes from your camera and fire the strobe on the fourth burst. All you need to know before you buy a strobe is how many pre-flashes your camera fires and purchase a strobe that covers that many pre-flashes.
