Off-camera slave triggered by built-in as wireless (with Pentax K-30)
About the issue
It seems that, although the Bower SFD926 flash works flawlessly as an on-camera flash, when using it off-camera in slave mode, and combined with the on-camera (perhaps built-in) flash in wireless mode (either master or controller) or in automatic mode, it fails to trigger the slave flash if set to high power (perhaps higher than 1/4).
The issue is that the on-camera flash emits a pre-exposure pulse, which the slave flash (Bower in this case) assumes is the trigger and outputs the burst of light. However moments later, during the actual exposure, the on-camera flash emits another pulse that should be the actual trigger; unfortunately if the slave flash (Bower) is set to a high power (perhaps higher than 1/4), it will not have enough power to output another burst of light.
The only solution (without involving extra hardware) is to either:
- convince the camera not to trigger the on-camera flash to emit the pre-exposure pulse; (unfortunately on my Pentax K-30 I was unable to do so;)
- configure the slave flash (Bower) to a low-enough power (perhaps lower than 1/4), so the slave flash is able to output two bursts of light in short intervals;
- configure the camera to use a delay, so that the interval between the pre-exposure pulse and the actual trigger pulse is long enough that the slave flash (Bower) is able to re-charge;
By using additional hardware, one can either:
- use another external on-camera flash in manual mode configured to the lowest power available;
- use a cable or wireless (optical or radio) trigger, which will transform the slave flash into an on-camera one, thus acting correctly;