You use the Red Eye tool and the Red Eye Correction adjustment controls to reduce the red-eye effect in the eyes of the subjects in your image. You use the Red Eye tool to place targets on the red eyes of the subjects in the image, and then you can adjust the radius and sensitivity of the target overlays using the Red Eye Correction controls. Aperture desaturates the red pixels within the target overlay area, reducing the effect.
Reducing red-eye in the eyes of the subjects in your image is as simple as targeting the red eyes with the Red Eye tool.

Select an image.
It’s a good idea to set the image to appear at full size (100 percent) to prevent image scaling from obscuring details. To display images at full size, click the Zoom Viewer button in the tool strip or the Full Screen view toolbar (or press Z).
Select the Red Eye tool in the tool strip or the Full Screen view toolbar (or press E).
The pointer changes to a target, and the Red Eye HUD appears.
Click a red eye in the image to place a Red Eye target overlay on it.
The Red Eye target overlay is placed over the red eye, and the red pixels within the Red Eye target overlay are desaturated.

Repeat step 4 until all of the red eyes in your image are corrected.
Aperture fixes red-eye in your images by desaturating the red pixels within the Red Eye target overlay area. It’s a good idea to fit each Red Eye target overlay to the size of the eye it covers. This prevents any red pixels in the skin around your subject’s eyes or in clothing, such as a scarf or hat, from being affected by the red-eye adjustment. You may also need to increase the size of a Red Eye target overlay to completely encompass the eye you are targeting if the image is a close-up. You can adjust the size of a Red Eye target overlay before and after it’s placed on the image.
Drag the Radius slider in the Red Eye HUD.

If you have a mouse device with a scroll wheel, rotate the scroll wheel.
The size of the Red Eye tool’s target changes.
You can also change the size of any Red Eye target overlay that you’ve already placed on an image.
Display the image at full size (100 percent) by clicking the Zoom Viewer button in the tool strip or the Full Screen view toolbar (or pressing Z).
Click the Red Eye target overlay to select it.
A hand icon appears to indicate that you can select the Red Eye target overlay.

In the Red Eye Correction area of the Adjustments inspector or the Adjustments pane of the Inspector HUD, adjust the Radius parameter by doing one of the following:
Drag the Radius slider.
Click the left or right arrow in the Radius value slider to change the size of the Red Eye target overlay by single increments, or drag in the value field.
Double-click the number in the Radius value slider, then enter a value from 3.00 to 400.00.

The size of the Red Eye target overlay increases as the parameter value increases.
When you target 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 large 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 radius 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.

Click the Red Eye target overlay to select it.
In the Red Eye Correction area of the Adjustments inspector or the Adjustments pane of the Inspector HUD, adjust the Sensitivity parameter by doing one of the following:
Drag the Sensitivity slider.
Click the left or right arrow in the Sensitivity value slider to change the sensitivity of the Red Eye target overlay by single-pixel increments, or drag in the value field.
Double-click the number in the Sensitivity value slider, then enter a value from –10.00 to 10.00 and press Return.

The area within the Red Eye target overlay where desaturation occurs increases as the parameter value increases.
After correcting the red eyes in your image, you can view the corrected image with the Red Eye target overlays turned off.
Select the Selection tool in the tool strip or the Full Screen view toolbar (or press A).
The Red Eye target overlays disappear, but the effect of the Red Eye adjustment remains visible.
Note: You can still make adjustments to the targeted red eyes with the overlays turned off, and the image is updated to show the changes.
Select the Red Eye tool in the tool strip or the Full Screen view toolbar (or press E).
In the Red Eye Correction area of the Adjustments inspector or the Adjustments pane of the Inspector HUD, click the Red Eye Tool button (with an icon of a red eye).
The Red Eye target overlays reappear.
Once placed, a Red Eye target overlay can always be moved.
Make sure the Red Eye tool is selected, then place the Red Eye tool’s target over the Red Eye target overlay you want to move until the target changes to a hand icon.
The hand icon indicates that you can drag the target overlay rather than place a new one.

Drag the Red Eye target overlay to the appropriate position over the subject’s eye.
You can always delete a Red Eye target overlay.
Select a Red Eye target overlay in the image, then click the Delete button in the Red Eye Correction area of the Adjustments inspector or the Adjustments pane of the Inspector HUD.

Command-click a Red Eye target overlay.

The Red Eye target overlay disappears.