Being a total newbie when it comes to uw photography (depending mostly on luck...)..
been thinking about getting a wireless strobe for my dig cam...
Opinion.....
Before discussing strobes, I would first ask what camera do you have. I would want to know if the camera offered manual control of aperture, shutter, and ISO. If it didn't, I might end the strobe questioning right there and suggest they upgrade the camera first.
Auto cameras are calibrated to capture images in air with two feet firmly planted on the ground. This is quite different than shooting through water while attempting to hover in any current. An auto camera will most likely assume a low light situation when submerged, resulting in shutter speeds too slow for hand holding underwater along with wide open apertures that wash out ambient lit background exposures. There's also the chance of the camera arbitrarily choosing to increase the ISO if manual control of that function is unavailable. All of these "out of control" auto functions add an unknown variable to the external strobe~aperture exposure equation. That is why, imho, it is best to avoid building an underwater rig around this type of camera.
Second question is what type of housing. Is it clear or aluminum? Does it have a bulkhead for a sync cord or will the camera optically trigger the external strobe, sending commands via the onboard strobe either with or without a fiber optic cable.
How will the user control the strobe's intensity. Does the user wish to use some form of TTL, Auto, or manual control of the strobe's output.
TTL works well with macro compositions of average reflectance. It gets trickier when close focus wide angle is the preference or if a shiny barracuda is the focus of attention.
Auto controlled strobes require the user to match the aperture setting of the camera to the strobe (or not!). The auto strobe is equipped with a sensor in it's head. The sensor's job is to collect reflected light sent from the strobe that has bounced back off the target. The drawback to the system is that it generally requires the strobe to be aimed directly at the target, potentially increasing the possibility of capturing backscatter by illuminating the water column between the lens and the target, especially when the target is in the center of the composition.
Strobes that fire manually are equipped with a dial on the head or attached to a controller that has a dial on it. These dials are timers. They control the strobe's influence on the exposure by how long the strobe is allowed to fire.
I would then ask questions regarding the camera's flash menu. Does the camera have a preflash? Does the camera have a slave flash option? The answers to these questions will help narrow the field.
Finally I would ask price range.
For more information on strobes, visit the digitaldiver strobe database, also known as the Strobe Finder.
http://www.digitaldiver.net/strobes.php
Data found in the database is from the manufacturers. The data is more relevant when you compare within vendors lines. OTOH, comparing the guide number from manufacturer "A" vs manufacturer "B" may not be as accurate due to different testing procedures.
There are also pop up windows filled with explanations of terms.
And finally the Strobe Finder includes manufacturers suggested retail prices. Street price will vary.
Hope this overview of strobes and the database helps. If you'd like more information about your camera, try dpreview.com, imaging-resource.com, or steves-digicams.com
regards,
b
