Option 1 (Merge)
When you get home, follow these steps to merge your location photos into your master library:
1) Copy the entire Lightroom catalog folder and your location library folder from your laptop to an external hard drive for transfer, or copy it directly to your master home or studio machine over a network. (Let’s keep the name of the location shoot folder “Location Photo Library” to distinguish it from your existing “Master” Photo Library.)
2) If you’re using an external hard drive, disconnect it from your laptop and connect it to the machine containing your master library and catalog. (Or, your external hard drive could be your master library drive, which is okay, too. This is the configuration I use for my photo library, rather than the computer’s internal drive.)
3) Back up your master Lightroom catalog! You can simply copy the .lrcat file to another backup location, or force Lightroom to do it for you. In Catalog Settings, set Lightroom to Backup Catalog when Lightroom next exits. Quit the application, and click the Backup button when the Backup Catalog dialog appears.
4) Open the master Lightroom catalog again. Lightroom should open the last catalog you were working with on that machine by default. If that isn’t your master catalog, hold down the Option key (Mac) or the Alt key (Windows) during launch, and Lightroom will allow you to navigate to a different catalog. Or simply choose File > Open Catalog and navigate to it.
5) Choose File > Import from Catalog, and navigate to the catalog (the .lrcat file) that you created on location and copied to your external hard drive. Click the Choose button.
6) When the Import dialog box opens, for File Handling, choose “Copy new photos to a new location and import” (Figure 2).
(If you don’t see the “Copy new photos” option for File Handling and only see the “Add new photos to catalog without moving” option, Lightroom can’t find the photo files, probably because you’ve changed their position relative to the catalog during the transfer to the external hard drive. This is one of the reasons why I suggest keeping these two folders together in one parent folder from the beginning.)
7) Click the Choose button to specify a location for the “Copy to” path. Navigate to your Master Photo Library folder and select it. Click the Choose button.
8) Click the Import button. If you’ve set up everything properly, Lightroom will import all the photos that are in your location catalog and put all the shoot folders where they belong in the master catalog’s Folders panel (Figure 3).