I work mainly on an iMac desktop and do full backups (all photos plus catalog) to several external HDs regularly. I also back up to a laptop, and to save time I'd like to know if I can do an incremental backup in this way: copy only the new photos, plus the lrcat file, to the laptop. Would this work, or do I need to copy everything every time?
The photos only need to be backed up once because Lightroom doesn't change the photos. Your master images always remain in their pristine state when they were imported. All of the changes are stored in the catalog. So the catalog will change every time you work using Lightroom. The catalog needs to be backed up on a routine basis. I have mine scheduled to be backed up once a week.