Sigma DP2 User Manual download pdf (Page 85)

HISTOGRAM

The histogram is a graph depicting the distribution of brightness values

in the image for each of the three color channels (Red, Green, and

Blue) (The histogram displayed in the Shooting Mode is the distribution

of tones in the image). The horizontal axis shows the brightness level,

with darker pixels towards the left side and brighter pixels toward the

right. The vertical axis shows the proportion of pixels at each level of

brightness.

By examining the histogram of the full image, you can gauge the overall

exposure of that image. You can also use the histogram to determine if

zoomed-in sections of an image are over or under exposed.

This histogram shows that the higher pixel

values are never used in the image,

indicating that the image is underexposed,

and therefore will appear dark. In general,

when the histogram is higher on the left side,

the image is mostly composed of dark

pixels, causing it to appear dark—either

because the image is underexposed or

because it is a dark scene such as night

shot or sunset.

This histogram shows a fairly even

distribution of pixel values, indicating that

the image is well exposed, with good

contrast. However, the histogram

distribution of a well exposed image will

vary greatly depending on the subject.

This histogram shows that many of the pixel

values are at their brightness limit,

indicating that some areas of the image

may be blown out. In general, when the

histogram runs off the right side, the image

will have many white pixels—either because

the image is overexposed or because it is a

bright scene such as the beach or snow.

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Sigma DP2 User Manual Page 85