or digital files, there are many file formats in use and no assurances that any will survive for 30 years. But most digital photographs today are stored in JPEG format, the compression standard used by most consumer digital cameras and supported by just about all the current imaging hardware and software. The digital-imaging industry is very unlikely to drop this support for it for a long time, even after better things come along. So store at least one copy of all your photos as a JPEG.
JPEG uses lossy compression, which means that a decompressed image is not exactly the image you started with. Shoot and store one copy of your images at the highest quality and resolution your camera allows. If you plan to manipulate your images, convert them to a lossless format, such as TIFF, while you edit, then save them back to JPEG when you are finished if you do not have enough space on your harddrive to keep them as TIFF