If you are going to use a digital camera to take pictures of tombstones, documents, etc. on a research trip, practice using the camera at home.
Try different kinds of books, different lighting, different times of day, etc. and see what works for you and what doesn’t.
The place to learn is at home when you have time, not a thousand miles away when rain is threatening, it’s late in the evening, and the last day of your trip.