While working in the Picture Library, there are many commands and program controls to make it easier to find and select the specific images you want to edit, display as a slide show, or print. In this and the following sections, you'll learn about them, starting with procedures for working with thumbnails.
Adjust thumbnail sizes. Whenever you like, you can change the size of the thumbnails in the Lightbox. You can make them very small to see every image in a packed folder or very large to get better idea of image quality and subject matter. To change thumbnail size, drag the slider beneath the Lightbox, choose a View menu command, or press a key shortcut.
Drag this slider to set thumbnail size.
Refresh thumbnails. If you think the thumbnails in the current folder don't accurately show recent edits, newly added images, or deleted files, choose Folder > Refresh Thumbnails. (This command can also be chosen from the folder's Actions button menu.)
Picasa checks for file changes and adjusts the folder's thumbnails as necessaryadding ones for new files, removing those of deleted files, and modifying thumbnail images to reflect recent edits.