Use the alternate Loupe
By default, Aperture displays the Centered Loupe when you show the Loupe to examine parts of a photo, but you can also use an alternate Loupe. You position the small ring of the alternate Loupe over the portion of the photo you want to see, and the large ring shows a magnified view. Depending on the details in the photo, you can change the size of the alternate Loupe and increase or decrease its magnification level. It’s useful for making quick checks for dust specks, flaws, fingerprints, or other issues. You can use the alternate Loupe on any photo or thumbnail in the Aperture library.
Show the alternate Loupe
Do one of the following:
Choose View > Show Loupe, or press the Grave Accent key (`).
Click the Loupe button in the toolbar.
To turn off the display of the Centered Loupe, choose View > Loupe Options > Use Centered Loupe.
The checkmark next to the Use Centered Loupe menu item disappears, and the Centered Loupe changes to the alternate Loupe.
Change the size and magnification of the alternate Loupe
To increase the size of the alternate Loupe: Choose View > Loupe Options > Increase Diameter, or press Option–Shift–Plus Sign (+).
To reduce the size of the alternate Loupe: Choose View > Loupe Options > Decrease Diameter, or press Option-Shift-Underscore (_).
To increase the magnification of the alternate Loupe: Press Shift–Command–Plus Sign (+).
Press these keys repeatedly to continue increasing the magnification.
To decrease the magnificaiton of the alternate Loupe: Press Shift-Command-Underscore (_).
Press these keys repeatedly to continue decreasing the magnification.