3.4

Chapter 16 Making Image Adjustments 351
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Channel pop-up menu: Choose a color channel to apply a tonal curve to from this pop-up
menu. You can also apply the tonal curve to all color channels combined, as well as show
separate color channel overlays when tonal curve adjustments are applied to individual
color channels.
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Auto Curves Combined button: Click this button to apply a tonal curve adjustment when
you want to correct contrast based on total luminance, without aecting the color cast of
the image.
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Auto Curves Separate button: Click this button to apply a tonal curve adjustment when you
want to correct contrast as well as remove color casts in the image.
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Black Point eyedropper tool: Use this eyedropper to set the black point in the image.
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Gray Point eyedropper tool: Use this eyedropper to set the gray point in the image.
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White Point eyedropper tool: Use this eyedropper to set the white point in the image.
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Add Point button: Click this button to use the Loupe to sample pixels in the image and then
add a point to the tonal curve for each color channel as well as the RGB tonal curve.
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In and Out elds: Enter the In and Out point values for a selected point on the tonal curve. The In
point represents the horizontal axis (x-axis), and the Out point represents the vertical axis (y-axis).
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Range pop-up menu: Choose a viewing range option from this pop-up menu. Choosing
Shadows restricts the view of the histogram and tonal curve from pure black to 50 percent
gray. Choosing Normal presents the view of the histogram and tonal curve from pure black
to pure white. Choosing Extended enlarges the view of the histogram from pure black to two
times pure white. Because some cameras are capable of capturing image information beyond
pure white, using the Extended range option provides controls for bringing that information
into the viewable image.
Working with the Auto Curves Buttons
You use the Auto Curves buttons to analyze the image and apply a tonal curve adjustment to the
image based on that analysis. This is a good way to make a quick correction to an image before
ne-tuning the Curves adjustment with the manual adjustment controls.
To automatically adjust the tonal curve of an image based on total luminance
When you want to quickly adjust the tonal curve of an image based on total luminance values—
red, green, and blue channels combined—you click the Auto Curves Combined button. Red,
green, and blue channels are adjusted by the same amount based on the total luminance. You
use the Auto Curves Combined button for luminance when you want to correct the contrast of
the image without modifying the color cast of the image.
Before Auto Curves Combined adjustment After Auto Curves Combined adjustment
1 Select a photo.
2 If the Curves controls are not shown in the Adjustments inspector or the Adjustments pane of
the Inspector HUD, choose Curves from the Add Adjustment pop-up menu.