Images that are already imported
Lightroom does a great job at trying to keep your collection organized and free from duplicates. During the import process, you’ll notice that there is an option in the File Handling panel on the right side that prevents you from importing images that have already been added to your Lightroom catalog. When you are just starting out with Lightroom, it’s a great idea to keep this selected.
When you try to import from a memory card or folder that you have already imported from, any of the images that are duplicates (that are already in your Lightroom catalog) appear in gray and will not be selected for import. If the card or folder has new images, those images will be visible and will already be selected, letting you specify where you would like them imported.
As a general rule, I advise photographers never to format their memory cards until after they have used up all of the cards they own. For example, if I have four memory cards (A, B, C, and D) and I make images on card A, I will import that card into Lightroom but will not format it. At the next shoot, I use card B and repeat the process. The following shoot? Card C.
Should something go wrong on my computer, I have a much better chance of recovering the images from the memory cards if I stagger the formatting in this manner. Working this way, you may forget to format a card and shoot with one that you’ve already imported. Thankfully, Lightroom is there to catch these kinds of things. Go ahead and import the images from the lesson02A folder that aren't duplicates.