Delete a roll of photos directly from iPod
Imported photos can also be deleted from the iPod disk while it is attached to a computer.
After you import TIFF images or movie files from an iPod photo into iPhoto with the "Delete items from camera after importing" checkbox selected, the photos and movie files will still appear to be present on your iPod.
iPhoto does in fact delete these files from the iPod, but it doesn't delete the thumbnail files that iPod with color display creates to indicate that you have imported these files into it from your camera or media reader. So although the files will still appear to be in your iPod, they're not. This doesn't happen with other image formats.
Instead of using the "Delete items from camera after importing" iPhoto option to delete photos from iPod with color display, use the Delete Roll function on your iPod to delete the photo and movie files—as well as the thumbnail files—after you've imported them into iPhoto.