Variable exposure during off-camera flash sequence

Discussion in 'Lighting Forum' started by Atom Ant, Sep 18, 2015.

  1. Atom Ant

    Atom Ant Mu-43 Veteran

    241
    Oct 24, 2012
    Melbourne, OZ
    Adam
    I have done very little work with studio lights, but tonight I gave it a crack at a local studio. It was a fun and learning experience.

    Our steampunk model Katy was doing some active poses, so I had the drive on 10 f/s. For each sequence, the first shot was a lot more exposed than the rest of sequence. Checking the histograms, the first shot would register right across, but the later shots would not extend past half way. The lights seemed like they were being triggered and they are supposed to be able handle better than 10 f/s.

    Earlier in the session I was getting short sequences (up to six frames) of black frames in the middle of extended sequences, but seemed to be as a result of asking too much of the processor - when I swapped to jpeg only I had no more of that problem.

    Unfortunately I can't show any examples yet. The images are all SFW, but the model agreement means that I can't publish until the model has seen them.

    I know this is pretty sketchy question, but any ideas what is happening?
     
  2. eteless

    eteless Mu-43 All-Pro

    Jun 20, 2014
    While the light may be able to trigger at a lower power setting 10 times a second I highly doubt the capacitors can fully recharge that fast at a reasonable power level, it's likely the capacitors were discharging from say 90% rather than 100% which makes a huge difference in peak light.

    This is assuming IGBT flashes, if they were older style monoblocks the capacitor is only charged to a preset % of capacity per flash and fully discharges (however I doubt this, they normally take longer to recharge and couldn't do 10 f/s).
     
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  3. Atom Ant

    Atom Ant Mu-43 Veteran

    241
    Oct 24, 2012
    Melbourne, OZ
    Adam
    The lights were Elinchroms, but I don't know how old or which models. They were set at a reduced power level and were able to recharge quickly enough for the other two guys, one Canon, one Nikon, who were both shooting at their maximum rates of 3-4 f/s. I was also advised to shoot at my max, but in hindsight, next time I'll throttle it back to DSLR speeds.
     
  4. eteless

    eteless Mu-43 All-Pro

    Jun 20, 2014
    It's a good brand, doesn't matter new or old they were likely built to high specs. The thing about studio equipment is it never really gets outdated, older equipment isn't a bad sign as quality is built to last.

    I would probably use the low drive speed rather than high, go for 6 and see how that works. It's still a huge amount of files to sort through at the end of the day :)