I do not have a new iMac G5 (iSight), so I do not have Photo Booth either. However, looking at Apple's new iMac pages and the Photo Booth 1.0 Help info leads me to believe that Photo Booth is an application for making snapshots rather than for editing existing images.
Check Photo Booth > Help on your iMac. If it does not tell you about editing existing images, you likely cannot do so.
Depending upon your experience level, image editor apps like PhotoShop or PhotoShop Elements can add the effects to your existing photos. Adding effects to existing images will require some effort, but it can be done. Unless your version of iPhoto is one of the very early ones, you can even set your iPhoto > General preferences to open your existing iPhoto images in your image editor app for easy access and editing from within iPhoto.
Because Photo Booth is only available with the iMac G5 (iSight) computer, you may find more help from Photo Booth users in iMac Discussions.
Check Photo Booth > Help on your iMac. If it does not tell you about editing existing images, you likely cannot do so.
Depending upon your experience level, image editor apps like PhotoShop or PhotoShop Elements can add the effects to your existing photos. Adding effects to existing images will require some effort, but it can be done. Unless your version of iPhoto is one of the very early ones, you can even set your iPhoto > General preferences to open your existing iPhoto images in your image editor app for easy access and editing from within iPhoto.
Because Photo Booth is only available with the iMac G5 (iSight) computer, you may find more help from Photo Booth users in iMac Discussions.
Apple Photo Booth App
Photo Booth is a software application for taking photos and videos with an iSight camera.It is published by Apple Inc. As part of macOS and iOS (on the iPad and iPad Mini available starting with the iPad 2). Photo Booth was released in October 2005 and was originally available only on Macintosh computers that had a built-in iSight camera running Mac OS X Tiger (version 10.4). You can use Photo Booth to add fun effects to your photos and videos, like a sepia or black-and-white look. In the Photo Booth app on your Mac, with the Take Photo button or Record Video button showing, click the Effects button in the bottom right. Click the browse buttons on the bottom of the window to see previews of the effects.
Photo Booth Heart Effect Online
Nov 28, 2005 8:49 AM