slave sensor flash unit - how do i get the timing right

YeGods · 07-11-2009 04:47PM #1

Hi all,

I've bought a pair 1600W external flash units. I'm having trouble trying to get them to flash in time with my canon 1000d built in flash. When I take a photo they do flash but don't seem to make any difference.
I have to use the built in slave sensors (triggered by the built-in flash) as I don't have a hot shoe flash. I've tried playing around with shutter times etc but they are still not hitting the mark. Anyone got any ideas on what I should be doing here.

ThOnda · 07-11-2009 04:58PM

There are few questions to be asked:

Do the flashes fire when you take the picture? Are they recharging?
If not, they are not triggered by your flash.
If yes, the problem is somewhere else.

Could you change your flash in custom functions for Second Curtain sync. by any chance (only if such function is supported by your camera)?

Are you 100% certain that the flash units are set to be triggered by external burst of light? Double check the position of the switches on the heads.

You can always get a sync. cable that goes into PC connector on your camera or to hot shoe adapter that could go onto your camera.

All the depicted hardware could be bought in local camera stores

Note - pictures are just googled one to picture idea of discussed products, there was no intention to put here links to specific stores or web pages.

YeGods · 07-11-2009 05:11PM

Thanks ThOnda,

I'm using a canon 1000d. The units do flash every time I take a photo.
I've already tried changing the flash to second curtain - no difference.
I did get it to work once of twice but only by playing around with exposure and blocking the second flash but it was impossible to recreate. It came with a sync cable but it's not compatable with the PC adapter in the camera. I'll try shopping around for the hotshoe adapter. Thanks for all fast reply.

Mycroft H · 07-11-2009 05:24PM

YeGods wrote: »

Thanks ThOnda,

I'm using a canon 1000d. The units do flash every time I take a photo.
I've already tried changing the flash to second curtain - no difference.
I did get it to work once of twice but only by playing around with exposure and blocking the second flash but it was impossible to recreate. It came with a sync cable but it's not compatable with the PC adapter in the camera. I'll try shopping around for the hotshoe adapter. Thanks for all fast reply.

Gunns cameras will have the said adapter

DaireQuinlan · 07-11-2009 05:42PM

I don't know how canon strobes work, I'm assuming in a similar way to nikon strobes. If they're fired in whatever the TTL mode is called they'll fire a couple of preflashes that the camera uses to meter the flash exposure. This happens before the shutter opens. Check that your external triggers can be set to ignore this pre-flash. If not then you'll have to use your on-camera flash in manual mode if possible.

YeGods · 07-11-2009 05:53PM

DaireQuinlan wrote: »

I don't know how canon strobes work, I'm assuming in a similar way to nikon strobes. If they're fired in whatever the TTL mode is called they'll fire a couple of preflashes that the camera uses to meter the flash exposure. This happens before the shutter opens. Check that your external triggers can be set to ignore this pre-flash. If not then you'll have to use your on-camera flash in manual mode if possible.

Thanks DaireQuinlan. I've tried that too but the shot still doesn't capture the light from the strobes. Looks like i have to find a hot shoe adapter with 2 outputs to sync the two strobes together.

pippatee · 07-11-2009 06:06PM

Try turning the Red eye reducer off in the custom functions ... it happened to me and that fixed it ...the flash prefires to reduce the size of the subjects iris, which in turn triggers the flashes prematurely ...

Phil

YeGods · 07-11-2009 06:20PM

Hi Pippatee, I tried that already too. Same result. I've tried everything I can think of. Maybe the strobes I bought are slow or else I am.

pippatee · 07-11-2009 06:35PM

What shutter speeds are you working at ... maybe you're shooting above your flash sync speeds ( i think it's 125th sec on the 1000d) ...if you are, then i will cause darkening on the photos ...

YeGods · 07-11-2009 06:54PM

pippatee wrote: »

What shutter speeds are you working at ... maybe you're shooting above your flash sync speeds ( i think it's 125th sec on the 1000d) ...if you are, then i will cause darkening on the photos ...

I've been trying fast and slow speeds but I've been keeping it slow for this experiment, around .5 as I've a stationary sebject - flower pot plant. I have found that if I set the flash to second curtain then i get the strobe light in the shot but only becsue the built in flash fires twice. I cover the built-in flash with my hand so the it's light doesn't reach forward but still triggers the slave sensors on the strobe units (after the initial metering flash) The experiment goes on.

DaireQuinlan · 07-11-2009 07:08PM

YeGods wrote: »

I've been trying fast and slow speeds but I've been keeping it slow for this experiment, around .5 as I've a stationary sebject - flower pot plant. I have found that if I set the flash to second curtain then i get the strobe light in the shot but only becsue the built in flash fires twice. I cover the built-in flash with my hand so the it's light doesn't reach forward but still triggers the slave sensors on the strobe units (after the initial metering flash) The experiment goes on.

What, so the pre-flashes are going off ? Maybe the strobes don't have time to recharge between the pre-flash going off and the main flash. To eliminate variables try to ensure that the built in flash is only firing once. Ie no pre-flash, no red eye reduction etc etc. Then try with second curtain sync (I'm assuming this is similar to nikons rear-sync which fires at the end of the exposure) and without second curtain sync. Try with slow speeds, 1/2 second, up to whatever your flash sync is. I suspect that using 2nd curtain sync is a bad idea if there's any delay at all between the on camera flash and the triggered strobes.

DaireQuinlan · 07-11-2009 07:11PM

Incidentally, I suspect your on camera flash is ALWAYS going off twice. Its just that you notice two distinct flashes when the camera is in second sync because there's a discernable delay between them.

YeGods · 07-11-2009 07:53PM

Thanks Daire - I'll check that out but i'd better sign off for now or I'll spend all night at this. Thanks again to everyone for their help. I'll let you know how I get on and what best settings worked for me.

uprising · 07-11-2009 09:00PM

If your camera is set to 2nd curtain sync there should only be 1 flash as the curtain closes, it shouldnt flash twice, I think you need to set your flash properly.
I'll google your set up and see if I can think of anything that may cause this.

EDIT: Sorry what is your setup, make, model of your flash heads and a photo if possible of your sync leads. But a slave should fire at the precise time as the triggering flash burst, not before or after, by reading this far I think your flash is sending out 2 flashes, play with your flash settings, I suspect the problem is with your built in flash.
Also is there a possibility that Infa red or the red light emitted from your camera may trigger the slave, but really if you can list your exact setup maybe it can be solved pretty easily.

smelltheglove · 07-11-2009 09:14PM

Have you tried with another camera? Maybe you should do that to rule out any problems. Is the sync cable just a little tight or loose? I had an issue with one being loose before but was able to tighten it up easy enough by putting it in between a scissors and tightening it ever so slightly. Which lights did you get, maybe someone here has had ecperience of your exact lights and could help you more.

slave sensor flash unit - how do i get the timing right

Comments