10D - Sync problem with studio flash...

[onehotrx7]

Hi Guys,

OK, here's a new problem... went to a studio shoot last night, we set up the lights, took some readings, using the 420EX bounced behind me to trigger the studio lights, settled on 1/90th @ F/11 - took about 20 shots, pretty much spot on, the white backdrop was nicely blown out and the model was coming through fine... then a third photographer turned up, and he didn't have external flash... but he did have a sync socket, so he was using the sync cable from the studio flash, and we stuck with triggering the studio gear as slave lights... then the studio flash stopped firing from our flashes, I proved it with the digital, showing that I could use my flash to light the subject, but I wasn't getting the extra light... the owner of the lights apologised, changed something and we went back to shooting... at that point, I started getting a very, very underexposed image... using the 420EX direct I was getting a good exposure, but the backdrop became clearly visible... hmmmm...

At this point I figured something was wrong, and that I'd managed to change some setting on the 10D... fiddled with the camera, tried some different settings - no way could I get the 10D to sync with the studio lights, although the 420 was making them fire... tried slower and faster shutter speeds, nothing... with a long exposure, and one of the other guys taking a shot, I captured the light from the studio flash fine... way overexposed, of course, but I could see it... reset the camera settings, tried again, still no sync...

By now it was getting frustrating... as much as I understand about photography, I couldn't come up with WHAT would cause the problem, so I grabbed my G2 out of my bag, put the 420EX on it, and took a shot... hopelessly overexposed, even at 1/1000th & F/8, but that's not unusual in a studio with the G2 - we could turn the studio lights down and get a reasonable exposure, but I wanted to shoot on the 10D... having verified in some small way it wasn't a 420EX problem, I tried the on camera flash on the 10D - it fired the lights, but there was still no sync with the studio flash...

I did the rest of the shoot using direct flash from the 420 on the 10D... it triggered the slaves fine, but simply none of the light showed through... I got some nice poses, but none of what I wanted from the shoot...

So, OK, here's the question - is it possible that somehow the studio flash was not working properly?? Could it have been triggering and shutting off too fast for synch?? Having tested when I got home, the 10D/420EX combo is working fine, as far as I can see - if I hadn't done the shoot in the studio I wouldn't be concerned about the camera at all... but if it's a problem I want to get it fixed... but if it's a studio light issue I don't need to be without the camera...

Any thoughts??

Cheers,
Stuart

[daveh]

onehotrx7 wrote:
So, OK, here's the question - is it possible that somehow the studio flash was not working properly?? Could it have been triggering and shutting off too fast for synch??

Am I being too simple-minded to ask if the pre-flash was disabled on the 420? Or could the studio light have been smart enough to ignore the preflash - but then it was reset to "dumb" mode?

[justme_dc]

Well, There are a lot of things that could have gone wrong. I don't have the specifics as to what brand the studio lights were so I'll give you the best guess of what could commonly go wrong. If I am way off the mark then chalk it up to my being criminally insane.

First things first I am fairly certian that your camera is indeed fine. No trips to the repair shop required.

I am assuming this was a multiple light set up also assuming that mono lights were used. Further I'll guess all the lights had built in slaves. Am I right so far? I hope so. This senario will work with Pack lights as well so hold on tight.

And away we go!

It is my experience that most mono lights have a function that disables the slave when a sync cord is plugged into it. This is very useful for a number of reasons I won't bore you with them here. So, when the sync cord got plugged in it caused that light to no longer trigger from your 420EX the other lights may trigger but you'll obviously get less light without the strobe that has the sync cord attached thus under exposure. Having a sync cord attached to the mono light/ powerpack will disable the slave feature even in the event that you disconnect the camera from the sync cord. I am speaking from experience here as I have had this very thing happen to me more than once when an assistant forgot to unplug a sync cord after doing some metering for me. Of course the only way to test this is to shoot with the lights again.

I hope That this clears up your problem. Lemme know if that was it. Good luck to you!

[onehotrx7]

Yep, you both got it... I remembered myself about the preflash after posting this to all places I could think of, after talking to another photog about the problem... initially it was set to ignore preflash, the sync cord overrode that setting, so it ignored flash trigger... putting the studio unit on sync + trigger evidentaly left it seeing the pre-flash on the 420EX... I think the G2 doesn't pre-flash on manual exposure...

Bingo, nothing wrong with the 10D... lesson learned... I now feel really sorry for the Eos user that won't know he got nothing until he get's his film developed, as his camera would have been pre-flashing for exposure too...

Live and learn - I still got some good shots!!

Cheers,
Stuart