Lightroom is actually more of an organizational software than an editing one. Essentially, Lightroom holds a virtual copy of an image in its catalog and only references the original when necessary. But if you move or rename an image, Lightroom loses track of it. And big problems ensue.
Here at My Lightroom is a Mess, we help a lot of folks out with their Lightroom organization. Here are the initial steps that we use to organize images. If you want assistance with this and all other aspects of organizing a Lightroom Catalog, you can book a free 15 minute session where we will look at your catalog together and determine what needs to be done to get it in order.
1. Identify Missing Files
Make sure you're in the Library Module using the grid view (press "G" on the keyboard). You'll recognize a missing image because the thumbnail will have an exclamation mark (!) or a white box icon on the top-right corner. To find your missing images all at once, go to Library > Find All Missing Photos.
2. Locate Missing Photos
Now we need to find the original file. It could have been renamed or moved or both. Click on the white box or the exclamation point in the top right corned of the thumbnail. Lightroom will prompt you to locate the image. Simply click on the button that says, "Locate". Lightroom will bring up a finder window based on the images last known location. Now you can navigate your computer, find the original image, and click on the button at the bottom right of the finder window that says, "Select".
3. Reconnect Missing Photos in Batch
Ideally, a folder of images has simply been moved. If you searched for all missing images (this is the search we did before in the Library module when we went to Library > Find All Missing Photos) then when you locate a single image, Lightroom will automatically relink all the other missing images from this single moved folder. Repeat this process for an image within each missing folder.
4. Relink Folders
If you've moved an entire folder, you can relink it using the Folders tool on the left panel of the Library Module. Unlinked folders show up with a question mark (?) on them. Right click on one of these folders and select "Find Missing Folder". A similar dialog box will appear, asking you to navigate your machine and find the missing folder. Click on the folder and then click the button that says, "Choose".
5. Renamed Folders and Images
We locate renamed images or folders in the same manner described above. However, batch relinking (step 3) does not work when images are renamed. Lightroom has no way to know the renamed image is the same as the original. So you would need to relink these individually.
Getting Lightroom into order is an essential part of your photographic workflow. Again, if we can help with your catalog, you can book a free 15 minute "getting to know you" session here.