Apple Aperture 2 - Manual (Page 377)

Chapter 15 Making Image Adjustments 377
III
Adjusting the Sensitivity of Red Eye Target Overlays
When you select a red eye in a picture, Aperture automatically chooses the area within
the target overlay circle where the desaturation is applied. In a few cases, the area chosen
by Aperture might be either slightly too wide or slightly too small (typically including a
few pixels in the eyelid skin, or missing a few red pixels inside the pupil). For these
difficult cases, you can adjust the Sensitivity parameter to change the area where
desaturation occurs. For example, dragging the Sensitivity slider to the left by one notch
decreases the size of the active area within the Red Eye target overlay by one pixel, and
dragging the Sensitivity slider one notch to the right enlarges it by one pixel.
Before Sensitivity adjustment
(the eyelids are desaturated) After Sensitivity adjustment