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| Increase | Decrease | |
| Contrast | ||
Without a doubt a Brightness/Contrast adjustment layer is the easiest way to make tonal adjustments. These controls work just like the adjustments on your television. Let's examine exactly what Brightness/Contrast adjustments do in terms of Curves.
To duplicate the effect of the Contrast slider in the Curves dialog box, increase in contrast moves the endpoints of the curve as shown below.
Increase Decrease Contrast
These adjustments are similar to adjustments of the input and output sliders in Levels. An increase in contrast will sacrifice detail, and a decrease in contrast will sacrifice tonal range. With Levels, however, you do have a histogram to view pixel distribution and can intelligently select cut-off points. With the Contrast slider you're operating in the dark.
Increasing and decreasing brightness adds the same value to all pixels. This effectively moves the transfer curve up or down as indicated below.
Increase Decrease Brightness
This also sacrifices detail and tonal range. The gamma slider in Levels, or shifting the midpoint in Curves, yields better results without loss of detail. The following dark image has been lightened using both Levels and the Brightness control.
There are better ways to increase brightness and contrast, and these methods should be used in preference to the Brightness/Contrast dialog box.
