You can select a photo against which to compare other photos in your project or in the library. The selected photo remains on the screen as you select and display other photos (alternates) to compare against it. The comparison feature is useful for making final selections of the best photos in a series or comparing two versions of a photo for correct exposure or highlights. When comparing photos, you can apply ratings and keywords and make adjustments to selected photos.
Set the Viewer to compare photos
Select a photo.
Choose View > Main Viewer > Compare (or press Option-O).
The compare photo appears on the left with a green border, and an alternate photo appears on the right.
Do any of the following:
To view a photo against the compare photo: In the Browser, select another photo, or navigate to another photo using the arrow keys.
To set the alternate photo as the compare photo and navigate to the next photo: Press Return.
To turn off the comparison feature and select the compare photo: Choose Edit > Select Compare Item (or press Option-Return).
To turn off the comparison feature and select the alternate photo: Choose Edit > Clear Compare Item (or press Command-Return).
You can also use these procedures to compare photos in full-screen view. For information about full-screen view, see Full-screen view overview.