Effect of Contrast Adjustment

Increasing the contrast control stretches the histogram out. Decreasing the contrast control compresses the histogram.

Contrast 0

Contrast +20

Contrast +40. This is just the right amount of contrast for this picture; the image extends the entire tonal range, with only a few pixels of pure white or of pure black.

Contrast +60. If you increase the contrast too much, the light pixels will "pile up" at pure white, destroying highlight detail, and the dark pixels will "pile up" at pure black, destroying shadow detail.

If the original scene had too wide a range of light intensity, the resulting image will have already lost highlight and shadow detail. The histogram will be clipped off at both ends.

Reducing the contrast in post-processing will NOT restore the lost highlight and shadow detail.