Apple Aperture - Manual (Page 124)

124 Part II Photo Editing
Working with a Selection of Images
At times, when you select a group of images, you may want to apply a change to only
the last image selected, and not change all the other selected images. Aperture
provides a Primary Only button in the control bar that gives you the option of applying
changes to the primary image in a group of selected images, leaving the rest of the
selected images unchanged. The primary image in a selected group of images appears
with a thick white border. You can change the primary image in a selection, without
changing the number of images selected, by pressing the Left or Right Arrow key.
Aperture is preset to have the Primary Only feature turned off, which applies your
changes to all the images in a selection.
To apply a change to only the primary image of a selection of images:
m Click the Primary Only button.
If you discover that a change was applied to only one image when you expected it to
change multiple selected images, check to see if the Primary Only button is selected.
Primary Only button