Adjusting brightness, contrast, and clarity

You can also
Add a point to the curve	Click where you want to add the point to the curve. Note: Adding more points to the curve lets you adjust its shape more precisely.
Remove a curve point	Drag the point to the left or right off the graph.
Move the active curve point more precisely	Press or hold down the Arrow keys.
Automatically adjust the photo’s contrast	Click the Contrast button in the Auto group box. Note: You can use this button when you’re satisfied with the photo’s colors but want to improve the contrast.
Automatically adjust the photo’s white balance	Click the Color button in the Auto group box. Note: You can use this button to find a black point and a white point in the photo automatically.
Automatically adjust both the contrast and the color	Click the Levels button in the Auto group box.
Set your own black, gray, or white point	Click the black, gray, or white dropper in the Colors group box to activate the dropper color. Then, move the cursor into the Before pane and click what you know to be a black, gray, or white point. The After pane (and the image window if the Preview on Image check box is marked) is updated.
Automatically determine the appropriate black, gray, or white point	Hold down Alt, and position the cursor in the Before pane (or in the image window). As you move the cursor over dark, medium, and light areas, the appropriate color dropper becomes active. Click to set that point.
Specify histogram clipping limits for the Auto Contrast, Color, and Levels buttons	Click the Options button. In the Auto Color Options dialog box, set percentage values for the Lower Limit and Upper Limit controls, and for the Strength control. Note: For the Lower Limit and Upper Limit controls, higher values result in stronger automatic settings, and lower values result in weaker automatic settings. Lower Strength values result in less clipping.
Reset all modified values to the original values	Click the Reset button located near the Colors droppers. You can also click the Reset to Default button located next to the Save Preset button.

On the left side of the histogram, look for a gap between the left edge and the point where the graph starts to rise. A gap shows that the darkest pixels in the image are not completely black. Drag the Low slider (the black triangle) to the point where the graph rises. The Low control displays the low position (from 0 to 254). The bottom control displays the percentage of pixels that are between zero and the low value; contrast for these pixels will be lost. As a general rule, keep the Low value lower than 0.1%.

You can create artistic effects by using the Output Max and Output Min controls on the left side of the histogram. The Max slider is the white circle within a gray square; the Min slider is the black circle within a gray square. To darken the image’s lightest pixels, drag the Max slider down. To lighten the image’s darkest pixels, drag the Min slider up. Even though you are dragging sliders along the vertical axis, the Max and Min values (from 0 to 255) affect the horizontal axis. All pixels outside the range are converted so that they fall within the range. You can choose another color component from the Edit drop-list and make similar adjustments.

The Histogram Stretch command pulls the darkest pixel down to black and the lightest pixel up to white. This command does not affect images that already span from pure black to pure white. If the original image has pixels that are very close to black and white, using this command will have a very small effect. If the original image is very flat (nothing close to black or white), using this command will have a strong effect.

You can also
Automatically adjust the photo’s contrast	Click the Contrast button in the Auto group box. Note: You can use this button when you’re satisfied with the photo’s colors but want to improve the contrast.
Automatically adjust the photo’s white balance	Click the Color button in the Auto group box. Note: You can use this button to find a black point and a white point in the photo automatically.
Automatically adjust both the contrast and the color	Click the Levels button in the Auto group box.
Set your own black, gray, or white point	Click the black, gray, or white dropper in the Colors group box to activate that dropper color. Then, move the cursor into the Before pane (or into the image window), and click what you know to be a black, gray, or white point. The After pane (and the image window if the Preview on Image check box is marked) is updated.
Automatically determine the appropriate black, gray, or white point	Hold down Alt, and position the cursor in the Before pane (or in the image window). As you move the cursor over dark, medium, and light areas, the appropriate color dropper becomes active. Click to set that point.
Specify histogram clipping limits for the Auto Contrast, Color, and Levels buttons	Click the Options button. In the Auto Color Options dialog box, set percentage values for the Lower Limit and Upper Limit controls and for the Strength control. Note: For the Lower Limit and Upper Limit controls, higher values result in stronger automatic settings, and lower values result in weaker automatic settings. Lower Strength values result in less clipping.
Reset all modified values to the original values	Click the Reset button located near the Colors droppers. You can also click the Reset to Default button located next to the Save Preset button.