Through interactive feedback using a Histogram, the Levels adjustment gives you live information about the tonal values in the active image. It's an excellent tool to perform overall tonal adjustments, and some color correction. Auto Levels is considered a quick fix color adjustment which, in some cases, works just as well as manually correcting color. However, with all the problems that exist in the average photo, it's always best to manually adjust an image. Since the Auto Levels command relies on information contained within the imageinformation that is sometimes inaccurateit's usually best to correct the image manually using the Levels Adjustment command.
Image menu, point to
Adjustments , and then click
Levels .
Channel list arrow, and then select the composite channel.
Input Level sliders to adjust the brightness level.
Output Level sliders to adjust the level of ink sent to the output device (printer).
OK .
Image menu, point to
Adjustments , and then click
Auto Levels .
If you don't like what you see, don't forget you have the ability to use undo.