Flash metering tricks/techniques?

Discussion in '35mm Cameras' started by z-one-b, Jan 8, 2004.

  1. z-one-b

    z-one-b Guest

    Hello,
    I have recently purchased a Canon 420ex speedlite to use with my Elan 7.
    I've managed to get pretty good prints at times and some pretty over-exposed
    ones at other times. It's the same old story for the over-exposed prints:
    the subject is in a dark room, maybe even wearing dark clothes, and has
    white skin. I've had the same problem with darker skined subjects. I know
    why this is happening - the camera's meter is thrown off by the darkness of
    the scene, and over-compensates to "lighten up" the scene to what it thinks
    is an acceptable level.
    Here's the question (finally!):
    What are your tricks or techniques to avoid over-exposition of a dark scene
    when shooting with flash?
    With the Elan 7, do you use the partial metering to meter off the subject's
    face (for example), then use FE lock, reframe the shot and shoot?
    For a sit-down portrait, would you meter off a gray card (once again using
    partial metering and FE lock)?
    ....or do you try to find the difference between the camera's suggested meter
    reading for the subject, then meter off a gray card...and then ajust the
    flash exposure compensation to the difference?
    Oh and one more thing (as if this post weren't long enough) - what
    instructions would you give to the lab when you get your photos finished to
    avoid that the machine compensates for ..ummm.. your compensations?
    Thanks!
    eqw
     
    z-one-b, Jan 8, 2004
    #1
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  2. z-one-b

    Bluenose Guest

    Bluenose, Jan 8, 2004
    #2
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  3. The first thing you need to determine is whether or not the fault is
    with the flash, or the processing. Line enlargers are notorious for being
    fooled by single faces in dark rooms, and most of them have much less
    sophisticated meters than your camera does.

    So examine the negative first, and see what kind of facial tones you
    have on them. If they fall somewhere in the middle range, the fault is not
    yours at all. Take the negatives back and have them reprinted correctly,
    for free. Then find a better lab. An ideal lab is one that requires *no*
    instructions to be able to figure out that you probably want the people in
    your photos to be properly exposed.

    If, however, the skin tones are truly dark on the negative, then you
    can start figuring what the camera is doing.

    The Evaluative Metering on the Elan series is pretty accurate and
    reasonably dependable for most shooting situations, but it can be fooled.
    Focus should be locked onto a mid-toned subject, and the subject should be
    large enough to take up at least a sixth of the frame. More is better. The
    camera will register the surrounding area as 'background' and will usually
    ignore it.

    Partial metering off of the face is one possibility, but you should
    probably open up a stop after doing so, since skin tones are lighter than
    the 18% grey that all meters default to. Be aware of how large the partial
    meter is, as well - if the subject does not fill it, this will skew the
    exposure.

    I would not try to compensate with the flash - instead, I would
    compensate with the camera. This will prevent problems where you actually
    have a good ambient light exposure for the background. But determining
    camera compensation still requires you to have an accurate meter reading in
    the first place, which puts you back at Partial metering or using a grey
    card.

    Canon flash modes are an arcane science. You can check out a slightly
    outdated FAQ at http://bobatkins.photo.net/info/faq30/flashfaq.htm to get a
    good idea of what happens - most, if not all, of this info should apply to
    the Elan 7 and 420EX.

    BUT, some things it misses:

    It makes good note of how many metering modes for the flash work off
    of the selected focusing point. It does NOT tell you that they fail when
    there is no focus point selected - manual focus without a specific point
    (eye-control still active, for example). In such a case, near as I have
    been able to determine, the camera defaults to an A-TTL mode, with no
    preflash, based on the entire frame. Diffusers and gels will NOT be
    compensated for in the flash output.

    You have to make sure that your active focus point is on the area you
    want properly exposed when the preflash goes off (in all modes that use
    it), otherwise the flash meter gets fooled. Thus, if you lock focus, then
    recompose the frame to put your subject outside of the focus point, the
    preflash will read something else. FE Lock is the key to this.

    Another thing to be aware of, unrelated to the problem you're having
    right now: The autozoom flash heads get fooled when you use the focal
    length in 'atypical' ways, such as 100mm macro lens. Your subject thus is
    close, but the flashhead is adjusted for a tight, distance carrying beam
    that may miss your subject. In such cases, go for tilting the bounce head,
    even just a smidgen (you will hear the head default to 50mm coverage when
    you do so), and use a bounce card if necessary.

    Good luck!


    - Al.
     
    Al Denelsbeck, Jan 9, 2004
    #3
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