Adjust Color Using Levels; Add Contrast To A Photo With Levels - Adobe Photoshop CS6 User Manual

2. (Optional) To adjust tones for a specific color channel, choose an option from the Channel menu.
3. (Optional) To edit a combination of color channels at the same time, Shift-select the channels in the Channels panel before choosing the
Image > Adjustments > Levels command. (This method does not work in a Levels adjustment layer.) The Channel menu then displays the
abbreviations for the target channels—for example, CM for cyan and magenta. The menu also contains the individual channels for the
selected combination. Edit spot channels and alpha channels individually.
4. To adjust the shadows and highlights manually, drag the black and white Input Levels sliders to the edge of the first group of pixels at either
end of the histogram.
For example, if you move the black point slider to the right at level 5, Photoshop maps all the pixels at level 5 and lower to level 0. Similarly,
if you move the white point slider to the left at level 243, Photoshop maps all pixels at level 243 and higher to level 255. The mapping affects
the darkest and lightest pixels in each channel. The corresponding pixels in the other channels are adjusted proportionately to avoid altering
the color balance.
Note: You can also enter values directly into the first and third Input Levels text boxes.
Adjusting black and white points with Levels Input sliders
5. (Optional) To identify areas in the image that are being clipped (completely black or completely white), do one of the following:
Hold down Alt (Windows) or Option (Mac OS) as you drag the black point and white point sliders.
Choose Show Clipping For Black/White Points from the panel menu.
6. To adjust midtones, use the middle Input slider to make a gamma adjustment.
Moving the middle Input slider to the left makes the overall image lighter. This slider adjustment maps a lower (darker) level up to the
midpoint level between the Output sliders. If the Output sliders are in their default position (0 and 255), the midpoint is level 128. In this
example, the shadows expand to fill the tonal range from 0 to 128, and the highlights are compressed. Moving the middle Input slider to the
right has the opposite effect, making the image darker.
Note: You can also enter a gamma adjustment value directly in the middle Input Levels box.
You can view the adjusted histogram in the Histogram panel.

Adjust color using Levels

1. In the Adjustments panel, click the Levels icon
2. In the Adjustments panel (CS5) or Properties panel (CS6), do one of the following to neutralize a color cast:
Click the eyedropper tool to set the gray point
Click Auto to apply the default automatic levels adjustment. To experiment with other automatic adjustment options, choose Auto Options
from the Adjustments panel menu (CS5) or Properties panel menu (CS6), then change Algorithms in the Auto Color Corrections Options
dialog box.
In general, assign equal color component values to achieve a neutral gray. For example, assign equal red, green, and blue values to
produce a neutral gray in an RGB image.

Add contrast to a photo with Levels

If the image needs overall contrast because it doesn't use the full tonal range, click the Levels icon
Shadow and Highlight input sliders inward until they touch the ends of the histogram.
or choose Levels from the panel menu.
. Then click in a part of the image that is neutral gray.
in the Adjustments panel. Then drag the
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