High Speed Sync issues

[craig.walton2]

I am trying to use my external flash (Sigma EF-530 Super) for fill outdoors. It is fitted on camera and I have enabled the HSS (aka FP) and use Manual mode with a SS of greater than 1/200 (ie 1/2000 etc).

The problem is that the HSS keeps resetting intermittently and therefore drops the shutter speed to 1/200 (my camera’s max sync speed – Canon 600D). I only notice it has done this when I check later and find lots of over exposed shots. I have tried to Google the answer but so far haven’t found anything.

I know that if I use Av and the camera sets the SS to sub 1/200 that the HSS will disable and wont re-enable automatically but I am using M. Many thanks in advance.

 

[Michael Sewell]

Is the flash securely fixed to the camera? If there is any kind of wobble or movement, it can interrupt the contacts so the camera gets a break in signal from the speedlight. This therefore would indicate to the camera the speedlight is no longer fitted, and would result in the camera switching from HSS to standard.

The natural reaction would be to tighten the locking ring (if fitted to the speedlight), but on some equipment with locking rings, I find it can actually lift the contact pins to the point that contact becomes tenuous, and can actually worsen the situation. I have this problem with one of my radio triggers in the studio. It's actually a fairly tight fit anyway, but tightening up the locking ring can cause the central pin on the transmitter to lift from the contact plate, and therefore no triggering of the flash heads.

 

[craig.walton2]

I will try to reproduce the problem with camera remaining static with no movement. I have since found out that on the Canon equivalent, you can select HSS to remain always on. I hope there is a way to do this on my Sigma.