spt29970
Contributor
HID lights are nice because they help you see and they help cameras to focus, but they are no substitute for a good strobe. Strobes are literally orders of magnitude brighter. A typical sync speed for a UW strobe is 1/200 sec (ie 5msec). The Ikelite DS125 full dump discharges a 110 Watt-second flash. The average optical power is therefore 110 Watt-sec/0.005sec = 22000Watt. Ignoring issues of beam angle and such, the strobe is 1000x brighter than that 20 Watt HID. The advantage of course is that the light is emitted as a burst, so the peak intensity is very high.
The other problem with HID lights for photography is that they create that annoying hotspot that Warren_L described. A diffuse focus light combined with one (or more strobes) is the way to go. With video, on the other hand, you really need a continuous light source, so HID or these new LED lights work well.
Of course, none of this will help with the original problem which was how to shoot deep wrecks. The brightest strobe in the world won't do much to light up a wreck. The are simply too big. Remember, the light has to go from your strobe to the wreck and back. If the visible part of the wreck is 30 feet away, the light has to travel 60 feet! With big wrecks the problem gets worse in a hurry. As stated earlier, the best bet is big glass, big sensors, and slow shutter speeds, all of which are hard with point and shoot cameras.
The other problem with HID lights for photography is that they create that annoying hotspot that Warren_L described. A diffuse focus light combined with one (or more strobes) is the way to go. With video, on the other hand, you really need a continuous light source, so HID or these new LED lights work well.
Of course, none of this will help with the original problem which was how to shoot deep wrecks. The brightest strobe in the world won't do much to light up a wreck. The are simply too big. Remember, the light has to go from your strobe to the wreck and back. If the visible part of the wreck is 30 feet away, the light has to travel 60 feet! With big wrecks the problem gets worse in a hurry. As stated earlier, the best bet is big glass, big sensors, and slow shutter speeds, all of which are hard with point and shoot cameras.