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Disabling Pre-Flash on GX1/GX7 for Use with Slave Flash?

Discussion in 'Lighting Forum' started by Turbofrog, Nov 23, 2014.

  1. Turbofrog

    Turbofrog Mu-43 Hall of Famer

    Mar 21, 2014
    So I recently inherited an old Starblitz 3600BTZ flash. I figured that since its trigger voltage is way too high to be safe on a modern camera that it was going to be useless...but it turns out that it has a slave mode. So that's cool. I was hoping to be able to use it off-camera with an optical slave set-up using the pop-up flash on my GX1.

    However, in testing I found that the off camera flash never actually shows up in the photos. The reason being that since it's an old film flash, it automatically fires when the metering pre-flash. There are plenty of kludgey ways to get around this, like turning my GX1 on to 2nd flash synchro mode, manually blocking the first metering flash (with my hand), and then exposing it again so that the 2nd synch can trigger the off-camera. But life is too short for something so stupid as that.

    So is there any way to disable the pre-flash on the GX1? (Or on the GX7, since I may upgrade to that in the coming months). It seems like a useful feature, and a bit of an oversight if I can't.

    Honestly I don't really need a flash, but I was hoping to have some fun with this, since it was free and is actually a pretty cool flash. Powerful, lots of manual settings, and good bouncing functionality.
     
  2. inkista

    inkista Mu-43 Veteran

    332
    Jan 13, 2012
    San Diego, CA
    Put the pop-up flash in Manual. On the GX7, it's [camera]-> Flash -> Firing Mode.

    Of course, this also means you have to explicitly set the power level of the pop-up; no preflash, and you can't have TTL.

    The other option, if you want to keep TTL and you don't need a lot of power from the remote flash, is to lower the power on the Starblitz until it can recycle from the preflash in time for the main flash burst. But no guarantees this will work; I just was able to shoot with a TTL preflash with my old Nikon SB-26 set to slave mode as long as I kept it to 1/2 power or lower. YMMV.
     
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  3. Turbofrog

    Turbofrog Mu-43 Hall of Famer

    Mar 21, 2014
    Thanks very much! I'm glad to hear that the GX7 has a fully manual flash mode. The GX1 doesn't have it (just TTL flash EV compensation).

    While I think my flash miiiight be able to recycle if I got some new batteries, with the rechargeable NiMHs that I have in it right now, it hasn't managed to recycle fast enough. Maybe if I used a very long exposure at a small aperture, but that's putting other constraints on the fun.

    Looks like yet another incentive to get that GX7...
     
  4. oldracer

    oldracer Mu-43 All-Pro

    Oct 1, 2010
    USA
    Another thing to consider is radio triggers. I just bought a Cowboy Studio set: transmitter and two receivers. It was open-box under $25 delivered (with Prime) from Amazon. It works great and eliminates the problem that the slave sensor must be line-of-sight to the master flash or at least it must get a good hit of light from a reflecting surface. That's more constraining than you might think. I don' mean to talk you out of the GX7 though. They are great cameras; I have two and have never regretted the decision nor have I seen any cameras since that I would prefer. Just be sure to get the Panny add-on eye cup.
     
  5. inkista

    inkista Mu-43 Veteran

    332
    Jan 13, 2012
    San Diego, CA
    ... or you could get a super-cheap Yongnuo flash and use S2 mode, where a single TTL pre-flash can be ignored by the optical slave. :) These days, there are a ton of options for cheap off-camera flash units, many of which have optical slave modes built in. I think a YN-560III goes for around US$70 on Amazon these days. And with a YN-560TX dedicated transmitter unit, you even have remote power control.

    And, of course, there are always radio triggers, which are desirable because they're not as line-of-sight or range limited as optical triggers. Just be sure you know the sync voltage of the Starblitz, because triggers also have a sync voltage limit.
     
  6. Turbofrog

    Turbofrog Mu-43 Hall of Famer

    Mar 21, 2014
    Haha, I could, but the reasons for upgrading to the GX7 go much farther than just wanting to use the flash (EVF, 2 control dials, IBIS, focus peaking, bigger grip, tilting screen, 2 stops more dynamic range...). Like I said, the Starblitz would mostly just be for messing around, so it's icing on the cake if I can get it to work with the GX7 with no additional hassles.

    The Starblitz apparently has a trigger voltage of 150-170V, and the half of the hotshoe is snapped off, which is another strike against radio trigger usage. I'm going to 3D print myself a handle with an embedded tripod mounting screw to go onto it and use it that way as an optical slave, probably with a Gorillapod.
     
  7. inkista

    inkista Mu-43 Veteran

    332
    Jan 13, 2012
    San Diego, CA
    Actually, the Yongnuo RF-603II/RF-605 triggers can withstand 300V (it's the earlier models that fried above 11V), so they'd be usable if you got a PC sync cable to connect one to the flash.
     
  8. oldracer

    oldracer Mu-43 All-Pro

    Oct 1, 2010
    USA
    Yes.


    I think it's dangerous to have that flash around, with its potential to damage cameras and radio triggers. I would either ditch it completely or at least use some epoxy glue to permanently seal the electrical terminals so it could never be accidentally connected. There are lots of cheap, decent flashes that come and go on CraigsList and there are reference tables on the internet that give trigger voltages for many of them. My route would be to replace it with something safe. A little patience and $50 should do it.