Canon MG2500 series Online Manual page 106

Images with widely distributed data
Move the Black-point Slider toward the highlight side, and White-point Slider toward the
shadow side.
Moving the Mid-point Slider
Move the Mid-point Slider to specify the level to be set as the middle of the tonal range.
Images with more data distributed to the highlight side
Move the Mid-point Slider toward the highlight side.
Images with more data distributed to the shadow side
Move the Mid-point Slider toward the shadow side.
Adjusting Histograms (Using the Droppers)
When you select a Channel and click the Black-point, Mid-point, or White-point Dropper,
the mouse pointer on the preview image changes to a dropper. Click a Dropper displayed
below the histogram to change the setting.
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