The Sharpen filter applies an adjustment that is frequently used in image retouching, and can vastly improve the appearance of your images.
1.
Click the Add button in the Adjustments Inspector and choose Sharpen from the pop-up menu.
2.
From the upper right of the toolbar click the Loupe tool to activate it.
3.
With the Loupe, mouse over the image to look at the details, concentrating on her eyes. You will notice that the focus is slightly soft.
4.
Click the Loupe tool again to deactivate it.
5.
In the Adjustments Inspector drag the Intensity slider of the Sharpen filter to the right to a value of 0.66 and drag the Radius to a value of 4.08.
Tip
You can also click on the left or right arrows beside the numerical value to increase or decrease your value by 1 increment.
6.
Mouse between her eyes and press Z to zoom in to your image.
7.
Enable and disable your Sharpen filter by clicking the checkbox. This allows you to view the image before and after.
Before
After applying the Sharpen filter
Notice that the focus and the detail of the image are vastly improved.
8.
Press Z to view the entire image in the Viewer.
Note
If you have distortion or noise in an image, particularly an image that was shot in low light, you can improve the image by applying Aperture's Noise Reduction filter. Take some time to experiment with the Noise Reduction filter on your own.