What are the advantages of using a different form of strobe initiator
Hi Tim,
Usually uw photographers see 7 reasons for going from pop-up flash to LED control:
1) Reflections, blinks through the port hole.
Pop-up flash produce strong light widely inside the housing. In many cases user can see some reflections on the image, because some light from flash goes to the dome port from inside. Usually it takes place in case the objective diameter is significantly smaller than port mount diameter. User even can see objective digital scale on the picture sometimes. I also have such defected shots in my stock. Manufacturers improve housings from year to year, but the issue is still not solved completely yet.
But the LED device solves the issue. It has narrow 8-15 degrees beam angle and it lights directly to the optical bulkhead.
2) Camera battery life
Pop-up flash consumes the battery rather fast. User have to change camera battery rather often. But impossible to change battery underwater during the dive. Also, in some dive trips can be difficult to recharge camera batteries. This is important for those people who make a lot of shots.
The LED device has battery life for 5-7 years, user need not think about the battery at all. LED devices save camera battery.
3) Pop-up flash overheating
After many continuose flashes inside the housing the pop-up flash sometimes switches off, because of overheating. There are thermo sensor inside the pop-up flash, which save it from overheating. When we have thermo shutdown, we cannot shoot, must wait for flash cooling.
But the LED does not heat, there is no temperature issue with LED devices.
4) Pop-up flash significant recharge time
Pop-up flash as classic xenon tube has a capacitor which requires significant time for recharging. User cannot shoot fast, he has to wait flash charging, some important shots can be lost. Continuose shooting (CL, CH) is impossible.
But the LED devices allow very fast shooting, cause LED has not any recharge time. Continuose shooting modes CL/CH are available with LED. I tested CH camera mode at 12 shots per second with Z-240 (at min power), it works perfect.
5) Pop-up flash max duration is not enough for uw strobe full range TTL control
Camera pop-up flash has a smaller xenon tube, than uw strobes have. Pop-up flash max fire duration is about 2 ms. But the full TTL range for Z-240 is 3.5 ms. So, pop-up flash cannot control underwater strobe in full required TTL range.
LED device have max fire time 4ms for Z-240, so the full Z-240 power is available for TTL control.
6) TTL accuracy by pop-up flash control sometimes is not very good
Camera flash xenon tube and Z-240 xenon tubes have different discharge curves, timings are little bit different for the concrete power values, that is why TTL accuracy sometimes is not very good under pop-up flash control. In some cases we almost don't see it, but sometimes we see it significant.
LED device does not have such issue. TTL LED Converter firmware is made for concrete Z-240 strobe type curve, that is why TTL accuracy is better this case.
7) Optical TTL control, Wire TTL control
Pop-up camera flash gives only optical TTL.
Some TTL Converters have complex TTL output: Optical TTL + Wire TTL. So, photographer can use fiber optic cable, or electric 5-pin cable. He also can use both at the same dive. These are extended capabilities for uw strobe TTL control.
