When you download pictures from the camera's memory card, format that card afterwards to make sure the next lot of pictures don't get fragmented when you take them. A lot of people have issues with pictures on cameras when they don't format after every shoot. It's caused by the new pictures not being lined up one after the other on the card and after a few photo shoots the card gets really messy. Then some of the pictures won't download or are broken. Formatting the memory card after each photoshoot keeps the card clean and you have less issues with corrupted pictures.