• Welcome to ScubaBoard


  1. Welcome to ScubaBoard, the world's largest scuba diving community. Registration is not required to read the forums, but we encourage you to join. Joining has its benefits and enables you to participate in the discussions.

    Benefits of registering include

    • Ability to post and comment on topics and discussions.
    • A Free photo gallery to share your dive photos with the world.
    • You can make this box go away

    Joining is quick and easy. Login or Register now by clicking on the button

Is the internal strobe used in external strobe TTL calculations?

Discussion in 'Sea&Sea Society' started by Matt S., Aug 26, 2010.

  1. Matt S.

    Matt S. Loggerhead Turtle

    # of Dives: 100 - 199
    Location: Kirkland, WA
    1,312
    44
    48
    I have another setup question about my DX-2G + YS-01.

    In TTL mode, is the internal strobe's output used at all in the overall TTL exposure calculation? I don't know what the exact sequence of events is.

    (If the internal strobe's pre-flash is blocked, the camera won't see any return from the pre-flash and it seems like it would have to max out strobe power and hope for the best. The external strobe would follow the internal's lead through the cable, so I would think that this would result in overexposure.)

    My home waters have very poor visibility and if it won't screw up TTL I would be much better off blocking the internal strobe, or using an IR filter on it so it passes no visible light. (I would keep the fiberoptic cable in place, of course.)

    If the internal strobe is not needed, and in fact can be harmful due to backscatter, why does the manufacturer not provide a means to block it when using an external strobe?

    If TTL does rely on the internal strobe I will probably have to shoot manual unless an IR-passing filter will let TTL work. In 10 ft vis, any light from the camera is going to cause backscatter.

    Thanks in advance if you've already solved this puzzle.
     
  2. Matt S.

    Matt S. Loggerhead Turtle

    # of Dives: 100 - 199
    Location: Kirkland, WA
    1,312
    44
    48
    Following up to myself--I got some replies elsewhere and did my own testing. You can and should cover up the internal strobe when using an external strobe in TTL mode. I was concerned that the internal pre-flash would still be important to the process, but it's not. Get out the duct tape!

    Be sure to put the fiberoptic cable adapter thing on first, and then put the tape on. If you just put the cable into the hole without the diffuser-adapter piece in place, TTL won't work as reliably.

    TTL even appears to work when the camera is set on manual, so you may not have to stick with aperture priority.
     
  3. marzum01

    marzum01 Angel Fish

    21
    0
    0
    Matt, thanks for confirming this. Did you ever find out if the strobe's TTL slave sensor can pick up infrared?
     
  4. Matt S.

    Matt S. Loggerhead Turtle

    # of Dives: 100 - 199
    Location: Kirkland, WA
    1,312
    44
    48
    I never did that test as the duct tape worked out well.
     

Share This Page