David Busch’s Nikon D7000 Guide to Digital SLR Photography104
WHY THE GRAY CARD CONFUSION?
Why are so many photographers under the impression that cameras and meters are cali-
brated to the 18-percent “standard,” rather than the true value, which may be 12 to 14
percent, depending on the vendor? You’ll find this misinformation in an alarming num-
ber of places. I’ve seen the 18-percent “myth” taught in camera classes; I’ve found it in
books, and even been given this wrong information from the technical staff of camera
vendors. (They should know better—the same vendors’ engineers who design and cali-
brate the cameras have the right figure.)
The most common explanation is that during a revision of Kodak’s instructions for its
gray cards in the 1970s, the advice to open up an extra half stop was omitted, and a
whole generation of shooters grew up thinking that a measurement off a gray card could
be used as-is. The proviso returned to the instructions by 1987, it’s said, but by then it
was too late. Next to me is a (c)2006 version of the instructions for KODAK Gray Cards,
Publication R-27Q, and the current directions read (with a bit of paraphrasing from me
in italics):
■For subjects of normal reflectance increase the indicated exposure by 1/2 stop.
■For light subjects use the indicated exposure; for very light subjects, decrease the
exposure by 1/2 stop. (That is, you’re measuring a cat that’s lighter than middle gray.)
■If the subject is dark to very dark, increase the indicated exposure by 1 to 1-1/2
stops. (You’re shooting a black cat.)
MODES, MODES, AND MORE MODES
Call them modes or methods, the Nikon D7000 seems to have a lot of different sets of
options that are described using similar terms. Here’s how to sort them out:
■Metering method.These modes determine the parts of the image within the 1,005-
segment sensor array that are examined in order to calculate exposure. The D7000
may look at many different points within the image, segregating them by zone
(Matrix metering), examine the same number of points, but give greater weight to
those located in the middle of the frame (Center-weighted metering), or evaluate
only a limited number of points in a limited area (Spot metering).
■Exposure method.These modes determine which settings are used to expose the
image. The D7000 may adjust the shutter speed, the aperture, or both, depending
on the method you choose.