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Thread: Flash-Differences between TTL and ADI

  1. #1

    Default Flash-Differences between TTL and ADI

    For those who interested in "Minolta-TTL and ADI".

    Infos are provided by twm47099 in yahoo group.

    TTL (on the 7): You AF. The camera uses one of the AF sensors. It
    selects the flash meter segment that corresponds to that AF sensor
    and gives that higher weight in its exposure calcs. The shutter
    opens. At the proper sync point the flash fires. The light from the
    flash bounces off the subject, returns through the lens (TTL),
    bounces off the film and hits the flash meter (in the mirror box
    region). When the camera detects that the proper exposure has been
    acheived it cuts off the flash.

    ADI: You focus. The "D" lens tells the camera how far the subject
    is. The camera tells the flash (lets use the built in flash for
    simplicity) what guide number (power) to use to put the right amount
    of light on the subject based on film ISO, aperture, distance. The
    flash fires and theoretically should turn off at the correct exposure
    without any TTL metering. This should be more accurate than TTL
    since TTL is affected by the subject and background reflectivity.
    However, whether Minolta uses some TTL when using ADI was the recent
    subject of some controversy. Likewise with the 3600 and 5600 ADI
    seems to require preflash. There was again argument about why that
    was necessary or not. (Possibly to calibrate the guide number of an
    add on flash?? Possibly to vote on the correct exposure --like the
    space shuttle computers???) Minolta's not telling.



  2. #2
    Join Date
    Jan 2002
    Bukit Batok West Avenue 2


    Well... I thought I read in the manual saying that the ADI uses some TTL factors as well......


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