Instruction manual

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immediately after a shot is taken, or later when single frames are being
reviewed.
Note: If your camera has a histogram feature, review the manual so that
you will interpret it correctly. Some cameras show the histogram ‘upside
down’ when compared to the histograms shown in this text; however, the
weighting (e.g., left side = dark) is usually the same.
The histogram is a simple graph that displays where all of the
brightness levels contained in the scene are found, from the darkest to the
brightest. These values are arrayed across the bottom of the graph from
left (darkest) to right (brightest). The vertical axis (the height of points on
the graph) shows how much of the image is found at any particular
brightness level.
The names of the five zones (or F-stops) containing the dynamic range
recordable by a camera is arbitrary.
A histogram that shows more weight at the left of the graph represents
a dark image (also called a low-key image); a histogram with more weight
to the right of the graph represents a bright (or high-key) image.
An image with a low-key histogram may be overexposed, and an image
with a high-key histogram may be underexposed, though this is not
necessarily always the case. For example, histograms of photos taken from
a high-wing aircraft such as a C172 usually shows more weight at the left
of the graph because the wing shadows the camera as you shoot pictures of
well-lighted targets on the ground. Your eye - not a histogram - should
always be your final judge.