a point to it. Then drag the point up or down to make
the corresponding brightness value lighter or darker.- In the middle of the luminance graph is a gray histogram
that’s scaled vertically to fit the square graph. Note that this
histogram is static; it always represents the image prior to
your modifications. - Near the bottom-left corner of the graph are two tools for
directly editing the luminance curve. The first is the point
tool. Click in the graph with this tool to add a point to the
curve, and then drag the point to bend the curve. The sec-
ond tool, the pencil, lets you draw freehand curves. For
example, if the curve flexes in a way that you don’t like,
switch to the pencil tool and draw directly inside the graph.
Available only when the pencil tool is active, the Smooth button (the
icon below the pencil tool) rounds rough corners in your graph. Smooth
is especially useful after Shift-clicking with the pencil tool, which draws
straight lines. If one click of the Smooth button doesn’t do the trick, click
the button again. In fact, clicking two or three times in a row is the norm,
not the exception.
- Introduced back in CS4, the targeted adjustment tool lets
you choose a spot on the image and move your mouse up or
down to reset all equivalent luminance values in the image. - When available, the Input and Output values show the co-
ordinates of the chosen point in the graph. Located below
the graph, Input tells the original brightness of the color; to
the left, Output indicates what the brightness will be when
you click OK. As with the Levels command, the brightness
of an RGB image is measured from 0 to 255.
Now that we have the cursory introductions out of the way, let’s
see how these options fare in a real-world project.
- Choose the targeted adjustment tool. Make sure the point tool
is selected in the lower-left corner of the Adjustments panel, so
that the targeted adjustment tool is available. Note that I call it
the “targeted adjustment tool,” but you won’t see that name if
you hover over the icon. I stole the name from Adobe Light-
room, where the tool made its first appearance, because it’s so
darn appropriate. We’ll use this tool to indicate input values
that we want changed to lighter or darker luminance values in
the image.
Correcting with Curves 207