Pentax K-R Operating Manual page 33

A histogram shows the brightness
distribution of an image. The horizontal
axis represents brightness (dark at the
left and bright at the right) and the vertical
axis represents the number of pixels.
The shape and the distribution of the
histogram before and after shooting
tells you whether the exposure level
and contrast are correct or not, and lets
you decide if you need to adjust the
exposure and take a picture again.
_ Adjusting the Exposure (p. 117)
_ Adjusting Brightness (p.207)
(n
x
"6
E_
Z
(Dark) _Brightness_ (Bright)
Dark portions Bright portions
Understanding Brightness
When the brightness is correct and there are no overly bright or dark
areas, the graph peaks in the middle. If the image is too dark, the peak is
on the left side, and if it is too bright, the peak is on the right side.
Dark image Image with few bright Bright image
or dark areas
When the image is too dark, the part to the left is cut off (dark portions with
no detail) and when the image is too bright, the part to the right is cut off
(bright portions with no detail).
Bright portions blink red and dark portions blink yellow on the monitor
when [Bright/Dark Area] is [_ (On).
_ Playing Back Images (p.82)
_ Setting the Playback Display Method (p.222)
_ Setting the Display for Instant Review (p.276)
Understanding Color Balance
Distribution of color intensity is displayed for each color in the RGB histogram.
The right side of the graphs look similar for images that have White Balance
adjusted well. If only one color is lopsided to the left, that color is too intense.
_ Setting the White Balance (p.200)