Pentax LX and Flash Question

Discussion in 'Pentax' started by Duncan Murray, Jan 1, 2006.

  1. Happy New Year!

    I am now the proud owner of a very nice Pentax LX, complete with winder
    and the AF-280T flash. And having explored the ambient light
    capabilities of this fantastic camera, I have a question about using
    the flash balanced with ambient light.

    The manual says to not use the flash with anything other than
    'Automatic' and 'X' settings, so my first question is, what happens if
    you use TTL auto flash with manual shutter settings of 1/30 and longer?

    My second question is, if the above is not a sensible way of using
    ambient light, what is the best technique for getting ambient light
    balanced with flash?

    Can the test function be used with the camera on TTL auto? Or does it
    just have to be on 'auto'?

    Can flash compensation can be carried out using the exposure
    compensation dial, while using the camera in manual mode?

    Many thanks in advance,
    Duncan.
     
    Duncan Murray, Jan 1, 2006
    #1
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  2. Duncan Murray

    dtong22 Guest

    Can the test function be used with the camera on TTL auto? Or does it
    I have 280T and istDL which is very different from your setup.
    The test function is definitely not for TTL . 280T has its own sensor
    and you have to switch on the test function separately.
    For my case the answer it is TTL even if I have manual shutter
    setting. In your case, no harm in trying it out.

    Hope this can be of some assistance.

    Daniel
     
    dtong22, Jan 3, 2006
    #2
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  3. Duncan Murray

    Cheesehead Guest

    This would be a good question to pose on PDML.
    You can see how to join the discussion at http://www.pdml.net .
    And I'll look forward to the answer as I'm also looking at
    a possible LX purchase.

    Collin
     
    Cheesehead, Jan 4, 2006
    #3
  4. Duncan Murray

    no_name Guest

    Great combination.
    I'm looking at the camera and the manuals right now.

    Should work fine with speeds slower than X-sync.

    According to the manual, the camera's "automatic" setting is going to
    set the "X-sync" shutterspeed to 1/50 when it detects the AF-280T flash
    installed on the hot shoe.

    With the flash set to TTL auto, the camera will control the flash so
    that it quenches when the subject is properly exposed. A slower manual
    shutter speed should give the background more exposure, but the TTL is
    intended to balance the exposure with ambient light.

    The manual X-sync speed is 1/75 sec.

    I believe the flash's TTL automatic function is intended to balance
    ambient light with flash.
    AFAIK, the LX doesn't have a TTL auto setting. There's only automatic,
    although I think the automatic **IS** TTL.

    The AF-280T has a TTL automatic function. When coupled with the LX, the
    AF-280T's output is controlled by the camera's auto-exposure sensor.

    The flash test function should work just fine.

    With the camera set to automatic & the flash to TTL Auto, you should
    also get a flash ready indication in the finder, as well as a flash
    confirmation.
    I believe the compensation dial only controls the exposure in automatic
    mode. In manual modes, it will just tell you compensation is set (red
    flag in viewfinder).

    In automatic, I expect exposure compensation should affect how the
    camera's exposure sensor controls the flash, but can't say for sure it
    will. Don't find that anywhere in the manuals for either the camera or
    the flash.

    But, I don't find where it WON'T control flash OR shutter compensation
    in manual either.

    The main thing manual speeds seem to do on this camera is give you a
    functional shutter from 1/2000 down to 1/75 (X-sync) if the batteries die.

    BTW, if you don't get a user's manuals with the camera, Pentax provides
    them in PDF format on their website.

    http://www.pentaximaging.com/files/manual/LX.pdf

    http://www.pentaximaging.com/files/manual/AF_280T_FLASH.pdf

    The manual is a good thing, because this camera has too many great
    features to remember them all all of the time.
     
    no_name, Jan 4, 2006
    #4
  5. Many thanks for the replies.

    My overall impression from reading these replies and looking at the
    internet, as well as results from the camera are:

    TTL flash can be used with 'Automatic' and X to set it to the sync
    speed - 1/75, and also manual speeds slower than this can be set, and
    the flash should still be TTL control.

    The test function only works on Auto Flash, and not TTL. This is
    probably because the camera doesn't know that you've pressed the test
    button, and so can't quench the flash like it would if you used the
    shutter.

    I don't have any evidence for this, but, in theory - flash compensation
    should be controlled by exposure compensation dial, while shutter speed
    will not be affected for any of the settings. This would be because
    the flash quenching is dependant on ISO, and exposure compensation
    affects the same system.

    What a clever camera!
    Duncan.
     
    Duncan Murray, Jan 4, 2006
    #5
  6. Duncan Murray

    Cheesehead Guest

    IIRC,
    You can also insulate the back-left pin.
    That's the quash pin.
    It should allow you to use TTL with a variable flash output.

    Collin
     
    Cheesehead, Jan 5, 2006
    #6
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