Adobe DNG Converter is a simple utility that lets you convert digital image files from a range of digital cameras into a digital negative or DNG format. Many digital cameras use proprietary file formats, which makes it difficult to move raw files between devices and open them. This utility converts those proprietary files into so that you can edit or view them in the software of your choice.
A handy tool for preserving photos
Adobe DNG Converter isn't as simple to use as the photo editing apps that casual photographers will be used to working with, at least at first. If you have some experience with other types of batch conversion utility, though, it'll be reasonably straightforward. The interface isn't as elegant as a native Mac app would be, but it gets the job done. You may find that DNG files don't have the same previews in Finder as other types of image files, but this is an issue with Finder. This tool doesn't have a lot of features, but it does exactly what you need it do: translate files from the proprietary formats used by cameras to a more versatile one.
Simple but effective
If you want to convert digital images from a camera to a more useful format, Adobe DNG Converter is a good solution. You'll need to check on the app's site to see if your camera's format is supported, but most are.