Nikon 3D Matrix Metering and Focus Points

Ever wonder why you can get different exposures on the exact same scene with your Nikon camera using 3D Matrix Metering? The meter and AF system are linked in a way that usually produces great results. But for landscape photographers, it can sometimes cause overexposure if you focus on dark parts of the scene, like a shady foreground.

Nikon’s 3D matrix metering is an advanced exposure system that evaluates the entire color image. The same scene can be exposed differently, depending on the location of the active AF point. When the AF point falls on a dark part of the scene, the meter tends to open up the exposure (brighten it). If the AF point is on a bright part of the scene, the camera will expose the scene slightly darker. This difference in exposure can be particularly important to landscape photographers, who usually choose a foreground object for the focus point. If the foreground is relatively dark, the camera will often blow out the sky.

The solution is to first focus on the dark object in the foreground, and then lock focus (I use the AF-On button technique for this). Next, move the active AF point to a bright part of the scene. This allows the meter to bias the exposure to preserve highlight details in the final image.

14 thoughts on “Nikon 3D Matrix Metering and Focus Points”

  1. Thanks as usual. Just wondering if your AF-ON focus technique will lock through a bracketed sequence. Does the focus lock hold for 5 or 7 shots?

  2. Yes, because focus “lock” is done by taking your finger off the button, so AF is effectively disabled during shooting. Lock = AF motor not running.

  3. Nice explanation.
    I do the same except in the reverse order: light-metering first, AF-lock, then focus, recompose and shoot.
    Of course, the AEL/AFL lock is used as an AEL-lock.
    I prefer this order, because once the light metering is done, you can recompose your photo at will. (as if I had gone to mode M for a while)

  4. Thanks for the explanation — this is a wheel I’ve been trying to invent, but by metering first, while using AF-on, withnow- understandably dubious results. Incidentally, it’s nice to see the much-maligned or neglected ViewNX2 being put to positive use — I’ve been using it in tandem with PhotoMechanic before getting to CNX or Lightroom, or direct to CEP and SEP.

  5. If you shoot on manual metering, you don’t need to do anything except set the exposure and focus – once. If you’re doing landscapes, you have the time to adjust the exposure perfectly. Why leave it up to the camera to decide on exposure values when you can see the image and its histogram as soon as you have taken the shot?

    Additionally, if you are really serious about the shot, you will have a tripod under the camera and use a remote shutter release. Surely, holding or pushing buttons will generate camera movement?

    I don’t mean to be a wet blanket, but I just don’t see any need to “play with the buttons” in a situation like this?

  6. I think that you’ve missed my point. Regardless of what Exposure Mode you’re in, the meter value is biased towards the active AF point. That is true for Manual, Aperture, Shutter, Program Auto. Therefore, it’s good to know how it works, regardless of how you choose to use the camera.

  7. Sorry, Jason. I was forgetting that I always use spot metering, therefore always fully metering exposure directly off the subject. So, in that case there is no bias to the active AF point required – only exposure adjustment for subject tonal value.

  8. Would you not get the same effect using Matrix Metering, and 3D Focus 39 points?
    Also, I notice that this same effect is present if you set a control point in CNX2, and move it from a dark area to a light area.
    Just an observation.

  9. Gary-
    No matter how many AF points are activated, only one is actually used to make focus/metering determination. The difference between single-point and dynamic focus area modes are that the camera may switch to a different point automatically. Either way, that point is used for the meter bias.

    Control Points have absolutely nothing to do with this phenomenon.

  10. Thanks for great explanation.
    How about if ones use manual focus lens?
    Does Canon got the same sort of connection between autofocus points and metering in their Eos bodies?

  11. At least with Nikon, the focus method doesn’t matter. Lenses that support matrix metering will allow you to bias the exposure point with the active AF sensor.

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