D200 Color Matrix Metering at night

Discussion in 'Digital SLR' started by Paul Furman, Nov 6, 2006.

  1. Paul Furman

    Paul Furman Guest

    D200 Color Matrix Metering at night still gets dark, not middle gray.
    Exif data says "Multi-segment" metering mode, I believe it was the
    default middle setting, not spot meter or center weighted. Aperture
    priority, f/16 on a tripod: exposures started at 8 seconds and lasted up
    to 30 seconds as the sun set but each frame still got progressively
    darker and I don't think this was entirely due to avoiding blown
    highlights in the lit up windows and full moon but perhaps?

    If you scroll down to the full set:
    .... some of them like that one don't have any intense highlights to
    protect and the sky could have gone plenty brighter... although I
    suppose the sky on that one is almost identical to this one:
    .... still I would think the matrix metering should be looking at the
    entire frame, not just the sky. The sky is nowhere near blowing out in
    the later dark one and 2/3 of the frame is underexposed. Is this normal?
    In this case I kind of don't mind how they look as a set but I was
    expecting more even exposures.

    Alright, one more thing to sort of answer my own questions:
    That's three manually equalized in exposure and the sky is indeed blown
    in the middle one but then the darker night sky is richer in the last
    one. Just interesting how the metering progrssivly made the darker night
    scenes darker exposures very consistently.
    Paul Furman, Nov 6, 2006
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  2. Light coming in through the viewfinder at the back perhaps?
    Nigel Cummings, Nov 6, 2006
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  3. Paul Furman

    Jeremy Nixon Guest

    What you're getting is pretty much as I'd expect from matrix metering. If
    you're expecting some middle gray, or something more like the results in
    your "equalized exposure" section, go with center-weighted metering perhaps.
    After all, that's not what the scene looked like, and the matrix meter is
    trying desperately to get what it looks like, not any middle gray.

    But in those situations I tend to ignore the meter altogether, as it's not
    really much help; I'll do a test shot starting from either the meter reading
    or whatever I think is right, check it on the LCD, and adjust from there.

    Then, in most cases, do a multiple exposure sequence and a merge to HDR in
    Photoshop, but that's another thing.
    Jeremy Nixon, Nov 6, 2006
  4. Paul Furman

    Paul Furman Guest

    Really? It's not what I thought but yes, the evidence is right there.

    I shot for about 20 minutes steadily as the sun set and conditions
    changed, I would have had to chimp the histogram for each 30 second
    exposure... but yes your right, center weighted or spot would have done
    what I expected, I just did not think matrix would make a night scene
    dark, I thought it tried to get the whole thing an average middle tone.
    How does the camera know it's night time?
    Paul Furman, Nov 6, 2006
  5. Paul Furman

    Jeremy Nixon Guest

    Yeah, that's pretty much what you'd have to do. Or else figure out how
    to make the meter do what you're expecting, which I suspect would involve
    center-weighted rather than matrix, judging from what you've indicated you

    You can short-cut the chimping by making the test shots artificially short,
    too -- set the ISO for 800 and the aperture for f/2.8 (or whatever wide
    open is for the lens you're using), and count how many stops that is
    different from the settings you're using for the real shots. Then you
    can make a test shot much more quickly, and adjust your final exposure
    by the right amount. So a test shot could just be a second or whatever,
    for a final "real" exposure of 30 seconds.
    What it does is measure various portions of the frame, and compare that
    with some kind of predetermined idea of what scenes giving those readings
    are like, and sets the exposure accordingly. I bet your shot with the
    moon looks like a sunset to the meter, for example, and indeed it appears
    to have been exposed as you would expose a sunset.
    Jeremy Nixon, Nov 6, 2006
  6. Paul Furman

    Paul Furman Guest

    Hmm, interesting. Maybe I will do more experimenting with spot metering,
    I assumed the matrix wouldn't try to outsmart me, I'll admit it normally
    works fine but it's frustrating to have complex subjective descisions
    made for me by the camera.

    Anyone know off-hand the best way to set AE-lock on a D200? Last time I
    looked for the D70 it was not a simple thing with AF-lock in the mix...
    a few different ways to set up the buttons. I'll want to point at
    something gray and lock the meter, then point at the focus point, lock
    that & recompose... not simple... I do sometimes more the active focus
    point, though it's a bit of a hassle.

    It would be interesting to have a better clue how the camera is making
    these descisions but sounds too complex and ambiguous to really get a
    handle on. I normally chimp the histogram with auto exposure and use EC
    from there. Ocassionally I'll then set that up in manual for a
    consistent look. I suppose manual isn't that bad if you use spot meter &
    the two dials while watching the meter reading in the viewfinder, a lot
    could be done on the fly without chimping with more intentional control
    of the exposure.
    Paul Furman, Nov 6, 2006
  7. Paul Furman

    Jeremy Nixon Guest

    It's pretty smart, but it can't be as smart as you. :)

    Center-weighted is definitely more predictable, of course, but the matrix
    metering does a good job most of the time.
    Set for manual exposure.
    Night exposure is all about experience, trial and error, and experimentation.
    After you do it a bit, you'll be able to "eyeball" it a lot better. I have
    my "func" button set to flip to center-weighted metering, but for tripod
    setups I don't usually bother with it, or really use the meter at all. If
    there's enough light for the meter to get a reading, I sometimes use that
    as my starting point, but it's rarely right on where I want to be for that
    kind of shot. That's just so far out of the range of "normal" and into
    "really difficult" that you can't expect it to get it right, I think.
    Jeremy Nixon, Nov 6, 2006
  8. It's possible to set it up so that the AEL button locks exposure only
    (not AF); you can set it up so that it either locks it only while it's
    pressed, or stays locked until you press again (and some other
    combinations). But if you're going to be spot metering, try manual.
    This is what I use most of the time, and it's very convenient.

    As an aside, I find the most convenient way to meter is spot and manual
    mode: I spot meter from the point which I want to be the brightest
    non-burned point, and set expose around 2 stops more than the meter
    reading (experiment, as it depends also on your raw converter and its
    settings, or jpeg settings if you're using jpegs).

    As for the matrix meter, I find it works OK most of the time (actually,
    in not too extreme situations it usually picks the same exposure I'd
    pick with spotmetering), but in more complicated situations it's hard
    to know what it's doing, so difficult to know if you have to compensate
    for it. It seems to be guessing what you are trying to photograph from
    brightness measurements at various points, so perhaps if the brightness
    is very low it decides it's a night scene etc. I suppose it's easy for
    it to decide if something is a light source and should be ignored (eg
    if something is brighter than a white piece of paper in full sunlight,
    it's obviously a light source etc). Or if the overall light level is
    low, perhaps with isolated bright spots, it exposes as if it is a night
    street scene. And so on. But anyway, with experience, spot metering or
    centreweighted is much more predictable, so if I have time, that's what
    I use.

    For night exposures, though, the main problem I have is that the meters
    just don't function reliably because the light is too low. So I use the
    technique Jeremy described (wide open, ISO 3200 for a test exposure,
    look at result, adjust until satisfied, calculate correct exposure at
    desired ISO). As always, experimentation is the best way to find out
    what works!
    achilleaslazarides, Nov 7, 2006
  9. Paul Furman

    Paul Furman Guest

    "AE Lock Hold" is the menu setting that lets me tap the AE-AF button
    once to lock exposure only. I can see in the viewfinder "AE-L" until I
    tap it again. Then half-shutter-press to lock focus (unless the
    continuous servo mode is activated on the front left side switch [C, S, M]).
    I think I can get used to spot metering with around EC +2 on whites,
    it's just a moment's more work with a tap on the AE lock in that setting.
    Eeek! Well, I can always flip it to matrix metering if I'm doing quick
    grabs and no time to think about things.
    Thanks for both of your thoughts on this.
    Paul Furman, Nov 7, 2006
  10. Paul Furman

    Don Wiss Guest

    By not using the lock button. I tried it on my D200. It was confusing as to
    when it was going to stay on or turn itself off. So taking the advice here
    I don't use it, but get the speed and F-stop in P mode, then switch to M
    mode. Then after the panorama I switch back to P (and hope to not forget).

    Don <www.donwiss.com/pictures/> (e-mail link at page bottoms).
    Don Wiss, Nov 7, 2006
  11. Paul Furman

    Ben Brugman Guest

    My working method :
    Matrix metering is faster than any other method I can do, for example
    spotmetering several points and working out the exposure. So I use
    matrix metering most of the time, and use the histogram to correct on

    If I have time to work out the exposure, I sometimes use the spot
    metering. For sports for example you are pressed for time taking
    the pictures, but you can prepare and work out the exposure
    before the actual 'event'.

    But as said most time I use matrix metering, not because it beads
    me with it's intelligence, but it sure beats me in time.

    Ben Brugman, Nov 9, 2006
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