Graphics Programs Reference
In-Depth Information
Taking advantage of Curves
The Curves adjustment is new to Aperture 3 and in our opinion was worth the wait. Using Curves,
you can modify the lightness or darkness of various areas of the image and increase or decrease
the contrast in different segments of the tonal range, as well as recover highlight data. To begin,
select Normal in the Range pop-up menu and RGB in the mode pop-up menu.
Initially, you see a histogram superimposed over the curve. To use curves, do the following, bear-
ing in mind that with any particular image you may need to omit a step:
Hold down the
Ô
key and begin to drag the White Point control (the triangle on the
right edge.)
The preview goes black, and as you move the white point to the left, col-
ored pixels appear indicating where data is being clipped in one or more channels. If the
pixels appear white, then data is being lost in all three channels. Move the control back
so that there is minimal, if any, clipping. With images that have specular highlights or
that are quite contrasty, you may not be able to fully remove the clipping this way, but
be certain you don't accidentally introduce any clipping.
Hold down the
Ô
key and begin to drag the Black Point control (the triangle on the
left edge.)
The preview goes white, and as you move the black point to the right, col-
ored pixels appear indicating where data is being clipped in one or more channels. If the
pixels appear black, then data is being lost in all three channels. Move the control back
so that there is minimal, if any clipping. With images that have blocked-up shadows or
that are quite contrasty, you may not be able to fully remove the clipping this way, but
be certain you don't accidentally introduce any clipping.
Click on the curve and drag it slightly up or down to lighten or darken pixels in that
area.
With curves, points closer to the tonality that you adjusted will be affected more
than those farther away.
To add some midtone contrast, consider adding a point about one-fourth of the
way up the curve and pulling this point slightly down.
Add another point about
three-fourths of the way along the curve and pull it up slightly. This increases the con-
trast in the middle half of the tonal range and decreases it slightly at the extreme ends.
Of course, you can set these points anywhere along the curve to add contrast to as small
or large a portion of the tonal range as you desire.
To remove a point that you've added, select it and then press Delete.
The point
disappears.
