Achieving Perfect Exposures in Digital and Film Photography 285
White Balance
White balance is closely associated with exposure and in some cases it is even more important
than exposure in digital imaging. It assures that digital images are not only properly exposed
but also have the correct tonal rendition. See Chapter 5 for details.
USING DIFFERENT METERING SYSTEMS
Metering Systems Built into Cameras
Metering systems built into cameras are of different designs, offering different metering
modes, different ways of showing and transferring the metering information, and different
degrees of automation. But they all measure the light refl ected off the subject and must be
used as described previously.
Average Metering
Average metering means measuring the entire, or almost the entire, image area seen in the
viewfi nder equally from side to side and top to bottom. The original H cameras offered the
averaging metering option with the meter reading based on a 45 37 mm center area, or
about 70% of the total image area. Average metering can be a good choice for fast shooting
and compositions without large dark or bright areas such as a white sky. But it is not a fi rst
choice for more critical work.
CentreWeighted Metering
The built-in meter measures a large part of the area seen in the viewfi nder but not equally.
The meter reading is based mainly on the subject brightness in the center portion of the
composition where the main subject is usually placed. The original Hasselblad H cameras
have a CentreWeighted mode that measures a 23 20 mm center area, about 25% of the
total area. Some Hasselblad meter prism fi nders used to have this system, but it has been
replaced by the more precise center area or Spot metering type in newer cameras and prism
fi nders.
Center Area Metering
In center area metering, the meter measures only the center area and allows a more accurate
metering approach. With this approach you know exactly what area of the subject is meas-
ured. Center metering is in the XPan cameras, an option in H cameras; in the 202 and 203
camera models, with approximately 75% of the light measured in the indicated center area;
and on the PME meter prism fi nders, where most of the light is measured within a 40 mm
center area. The latest H camera models offer two center metering modes both measuring
a center area of about 20 23 mm which is about 25% of the total image area. The centre
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