Hy to everyone!
I've read that my D70 is able to synchronize with a strobe faster then 1/500s. I'm using an iTTL Ikelite housing and two DS125's. On my last trip, shooting sunbursts, I tried to go faster then 1/500s but it didn't work.
Jordi
My first thought was, why would you need to do that!
That was my second thought as well!
You don't need to use a flash to shoot sunbursts. If you want to use one, stop down, and use the lowest ISO.
I can't think of many situations UW where one would need the stopping power of 1/500 second, and those times would have to be very unique in that if you are using a flash as a primary light source, the type of things that one would be shooting are high speed action shots like a barracuda hitting prey at 40mph.
In those types of situations you would have to be REALLY on the ball to capture such an image, while evenly lighting the subject, and keeping it in focus. A WA lens would likely be necessary to provide better DOF, and anticipating this type of action is difficult. Using a shutter speed of 1/750 means that the subject needs to be close (if using flash) or the lighting better be VERY exceptional.
Why can't DSLR camera's sync at higher shutter speeds? It is because they use a horizontal focal plane shutter to control the shutter speed rather than just turning the sensor on and off like a PnS style camera does. Shutters are more accurate than controlling the exposure with the sensor at high speeds, and for high frame rates attempting to turn the sensor off-on-off-on-off is problematic.
A horizontal focal plane shutter travels across the sensor and at high speeds the entire sensor will never be receiving light at the same instant. The shutter has blades, and these flip open, and closed, and they travel from left to right, or versa visa. At slow shutter speeds the blades will all be open at the same time, and that allows the camera to SYNC the flash so it fires while all the blades are in the open position. At speeds beyond 1/250 of a second the blades are never open all at once, so there is no opportunity to sync the flash without doing something funky like using modes such as FP.
The Nikon D1x, and D70 are unique in that they used the sensor to control shutter speeds at lower than 1/500 of a second. This allows them to sync beyond the shutter speed of 1/250 as the shutter opens for 1/250 when the 1/500 second speed is selected, but the exposure is controlled using the sensor. Beyond 1/500 the shutter is used, and sync speeds beyond 1/500 are not possible.
So back to my original question, what are you shooting UW using flash as a primary light source where the shutter needs to be faster than 1/500?
