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Help me understand STTL with TG-5

Discussion in 'The Olympus Outlet' started by Bernhelm, Nov 19, 2019.

  1. Bernhelm

    Bernhelm Angel Fish

    # of Dives: 100 - 199
    Location: San Francisco, CA
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    I'm using two Inon s2000 strobes with my tg-5, and my images tend to be a little blown out. Using the recommended settings from the Backscatter videos - flash on fill-in, exposure to -1.0 to -2.0, etc.

    I have a Backscatter air lens so I'm using the flash cover that it comes with (its black plastic, so it doesn't allow any camera flash through, which should be a benefit)

    Something I'm not quite understanding is how STTL works - from what I've read online, the camera does a preflash and uses that to determine "how strong" the real flash should be. The strength of the real flash is detected by the strobes and they adjust their strength based on the flash strength.

    If this is the case, then doesn't my setup cause the preflash to *not* register any real data to the camera, as if everything is dark even with the highest flash setting? Does that cause the STTL strobes to then fire at full strength, all the time?

    Or am I missing something here? Appreciate any info and advice!
     
  2. Steelyeyes

    Steelyeyes Manta Ray

    # of Dives: 200 - 499
    Location: Redmond Wa
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    Maybe that's why my macro shots are overexposing. Next time I'll take the air lens off to do those. I have the stock diffuser on with a fiber optic adapter but I'm sure the lens is blocking most of the preflash so the camera can't see it.

    I won't be diving again until March but I'll make a mental note. :)
     
  3. Barmaglot

    Barmaglot Manta Ray

    # of Dives: 100 - 199
    Location: Israel
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    If you're shooting in TTL, then pre-flash cancellation on the S2000s should be off - both strobes should flash on the pre-flash for the camera to evaluate it, then again on the main flash. Pre-flash cancellation is used when the on-camera flash is TTL-only (always flashes twice per exposure) and you want to run the strobes in manual power mode - in that case, you want to ignore the first flash and trigger on the second, but if you enable that setting when both camera and strobes are working in TTL then the camera won't get much (or any) return from its own flash, evaluate the scene as needing lots of light and fire the strobes as hard as it can, producing overexposure.
     
  4. Bernhelm

    Bernhelm Angel Fish

    # of Dives: 100 - 199
    Location: San Francisco, CA
    22
    8
    3
    Interesting! So, which mode is the "Fill-in" flash setting for - is that the correct TTL setting? I'm pretty sure you turn that off if going Manual strobes (and for inon S2000 that also means putting in the magnet button)
     
  5. Bernhelm

    Bernhelm Angel Fish

    # of Dives: 100 - 199
    Location: San Francisco, CA
    22
    8
    3
    Oh okay, I think I get it now - in STTL, the sequence goes like this:

    1. Camera does a preflash
    2. Strobes sense this and also do a preflash
    3. Camera senses the light from the strobe preflash (through the lens) and adjusts its flash power accordingly
    4. Camera does regular flash at adjusted power
    5. Strokes sense this and do regular flash, adjusting based on camera flash power
    6. Image is lit by strobes regular flash
     
  6. Chris Ross

    Chris Ross Manta Ray

    # of Dives: 200 - 499
    Location: Sydney Australia
    503
    165
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    You are using fibre optic cables?, might be stating the obvious but you refer to it as a flash cover - not a fibre optic adapter and you say: "then doesn't my setup cause the preflash to *not* register any real data to the camera, as if everything is dark even with the highest flash setting?" The fibre optic cable relays the preflash and main flash to the strobe so it's not impacted by having the air- lens on.
     
  7. JackConnick

    JackConnick Optical Ocean Sales ScubaBoard Business Sponsor ScubaBoard Supporter

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    You don't say it, but turn off auto ISO and set it to like 100 for macro and 400 for wider shots. Auto ISO will cause exposure to do all sorts of crazy things.
     
    coralcruiser likes this.
  8. coralcruiser

    coralcruiser Dive Charter

    # of Dives: 500 - 999
    Location: Chandler, Arizona
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    Make sure the fo cable is attached from strobe to camera and set strobe to sttl.
    Have attached inon s2000 info to help. I shoot sttl but use the ev controller on the camera to obtain a darker background when needed.
     

    Attached Files:

  9. Bernhelm

    Bernhelm Angel Fish

    # of Dives: 100 - 199
    Location: San Francisco, CA
    22
    8
    3
    Thanks, yup I'm using fiber optic cables (inon style d cables from backscatter) and iso set at 100 for macro and 200-400 for wide.
     
  10. Bernhelm

    Bernhelm Angel Fish

    # of Dives: 100 - 199
    Location: San Francisco, CA
    22
    8
    3
    Nice to see that diagram - interesting that you can do + 3 clicks in one direction and - 5 clicks in the other.

    I also noticed that quality of fo cable makes a difference. I had one strobe using an inon cable from backscatter and the other using a cable I had from an old sealife digital pro flash attached to an inon adapter. The strobe using the sealife cable was way weaker than the inon cable one and some of my docs weren't evenly lit. Buying another inon cable so they are both using them before my next trip.
     
    coralcruiser likes this.

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