Manual Metering; Exposure Lock - Nikon D5100 Experience Manual

Nikon D5100 Experience
Metering is used to determine the exposure values of several important parts of the scene, and
then the desired exposure is determined and then manually set using Manual Exposure Mode. In
this way Spot Metering Mode is used to turn your camera into a light meter, as a tool to
determine proper exposure of a subject or scene before switching the camera to Manual Mode
(M) for a controlled studio shot, a critical shot, or a series of shots where the lighting is not going
to change.

Manual Metering

A fourth metering mode is manual metering, which isn't actually a mode in your camera, but is a
method of metering. This is where you use a light meter or use your camera as a light meter
(such as described at the end in the Spot Metering section above) and then manually set your
exposure based on the meter readings. This is used when you want ultimate control of the
metering and exposure.
An example of a critical exposure that will vary depending on which metering mode you use and
where you meter in the scene is an image of a bride and groom. The bride is typically in all
white, and the groom may be in a black tux or dark suit. If you are using Center-Weighted or
Spot metering and meter the exposure on the bride, the camera will most likely underexpose the
image and the nice white dress will turn to grey in the photos and the groom's suit will turn into
a pool of deep, dark black. If you use Center-Weighted or Spot metering and meter on the
groom, the camera will most likely overexpose and the dark suit will become a medium grey
suit, and the bride will disappear into a blown-out blob of white. This is just an example to help
you realize the differences and importance of metering modes. It is quite possible that Matrix
Metering will capture this situation just fine. But be aware that there are situations where it is
critical that you know how the metering modes of the D5100 work, and make a decision for
which one will serve you best.

Exposure Lock

As discussed in the Custom Settings section, with the default settings of your camera, the focus
but not the exposure is locked when you press the Shutter-Release Button halfway. The
exposure meter begins metering, but exposure is not set until you press the Shutter-Release
Button fully and take the shot. But there are situations where you may wish to lock the exposure
before taking the shot or for taking a series of shots. In Custom Setting f2 I recommended that
the AE-L/AF-L Button be set to exposure lock – AE lock only or AE lock (Hold). This way you
can lock exposure and focus independently of each other.
A situation where you may wish to use this is in conjunction with Center-Weighted Metering or
Spot Metering. You may wish to meter for a specific area of the image, such as a person's face,
and then recompose the frame before taking the shot. The face or area you wish to meter is thus
no longer in the center – the area being metered by the camera for exposure – and thus if you do
not lock the exposure you desire, the camera will meter for the wrong area when the shot is taken
and possibly underexpose or overexpose the image (see Figure 31). Or you may be taking a
series of shots of a particular scene that contains a wide range of bright highlights and dark
shadows. You may carefully meter for the area you want properly exposed and lock in that
exposure setting, and then you can take the series of photos. If you set the AE-L/AF-L Button
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