Sigma SD1 User Manual download pdf (Page 94)

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

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 over-all

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 SD1 User Manual Page 94