Results 1 to 11 of 11

Thread: ETTL and over-exposed

  1. #1
    Moderator
    Join Date
    Jan 2002
    Location
    Singapore
    Posts
    1,165

    Default ETTL and over-exposed

    I know this sounds dumb, but what really caused a shot taken with a flash (Canon 550EX) in E-TTL mode, mounted with off-camera shoe cord 2, and the camera manually set at 1/60 F5.6 to be over-exposed? Is it because of the wrong metering setting? (Center weighted average vs partial vs evaluative)?

  2. #2
    Senior Member
    Join Date
    Feb 2002
    Location
    Singapore
    Posts
    3,644

    Default

    This should be an issue of exposure. Camera meters are not smart enough yet. Although in many cases a good exposure is expected, under difficult conditions (e.g. dark background or large white subject), the meters are likely fooled either wide open with dark background or underexposed with large white subject. That's why we need to compensate flash in the same way as we compensate exposure. Personally I found flash is a challenging topic in photography. Even the most sophisticated system cannot guarrantee correct exposure all the time.

  3. #3
    Senior Member
    Join Date
    Jan 2002
    Location
    Singapore, Singapore, Singapor
    Posts
    6,405

    Default

    AFAIK, Canon metering system for E-TTL is tied to the active focussing point. If you focus on something then recompose, you will get over/underexposure depending on where the AF point is pointing now. Solution is to explicitly preflash before exposure and before you recompose.



    Regards
    CK

  4. #4
    Moderator
    Join Date
    Jan 2002
    Location
    Singapore
    Posts
    1,165

    Default

    Thanks. It makes sense now. No wonder some shots are OK but some are not.

    I just tried the preflash option and indeed it solves the problem.
    Last edited by rty; 20th September 2002 at 09:19 PM.

  5. #5
    Senior Member
    Join Date
    Feb 2002
    Location
    Singapore
    Posts
    3,644

    Default

    Yes, preflash indeed helps when need to recompose.

  6. #6
    Senior Member
    Join Date
    Jan 2002
    Location
    Singapore, Singapore, Singapor
    Posts
    6,405

    Default

    Originally posted by tomshen
    Yes, preflash indeed helps when need to recompose.
    You just have to make sure your subjects does not think that you have ALREADY taken their photo.

    Regards
    CK

  7. #7
    Senior Member
    Join Date
    Feb 2002
    Location
    Singapore
    Posts
    3,644

    Default

    Originally posted by ckiang


    You just have to make sure your subjects does not think that you have ALREADY taken their photo.

    Regards
    CK
    Yes, it IS a problem if I preflash to animals/birds/insects sometimes.

  8. #8

    Default

    Been there, done that. Aim at medium tone object, preflash to FEL. Then focus, then recompose.

    I sold my 420EX and now use the $38 Achiever 260T (tested 4V trigger voltage) at the blue auto setting (lowest). Set shutter speed to 1/200, aim and shoot. No worries, consistent exposure.

    And, by the way, when you need slaves, you don't need to worry about an E-TTL preflash screwing up your slave triggers. Of course, you need to cover the on-camera flash with some unexposed slide film. If you need some, pm me and I'll point you in the right direction.

  9. #9
    Senior Member
    Join Date
    Feb 2002
    Location
    Singapore
    Posts
    3,644

    Default

    Originally posted by StreetShooter
    I sold my 420EX and now use the $38 Achiever 260T (tested 4V trigger voltage) at the blue auto setting (lowest). Set shutter speed to 1/200, aim and shoot. No worries, consistent exposure.
    This is new to me, can post some results pls?

  10. #10
    Senior Member
    Join Date
    Jan 2002
    Location
    Singapore, Singapore, Singapor
    Posts
    6,405

    Default

    Originally posted by tomshen

    This is new to me, can post some results pls?
    Reason is simple. The Achiever he used is set in AUTO mode, which is non-TTL. In this mode, the flash uses its own sensor to measure exposure, instead of the active focussing point. This sort of sensor usually measures roughly the whole scene, instead of one small point. So you can actually get more consistent exposures, depending on situation. And of coz, it doesn't pre-flash.

    If subject is out of flash sensor range, (very possible if you use flash extenders), exposure will not be accurate.

    Regards
    CK

  11. #11
    Senior Member
    Join Date
    Feb 2002
    Location
    L2TPYSG
    Posts
    4,057

    Default

    hmm so a vivitar 285 can do the same? since it's auto too...
    what's the slide film for huh? block what pins?
    "I'm... dreaming... of a wide... angle~
    Just like the ones I used to know~"

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •