Actually solo, I'm partially right. .tif and .tiff files ARE compressed , but it's a lossless compression. http://en.wikipedia.org/wiki/Tagged_Image_File_Format
.RAW files are just that. Raw. They are the image directly from the sensors on the camera. If you have a program that can download the .raw files from the camera, that's the highest quality image you can get. Then you can change it to any format you like from that. http://en.wikipedia.org/wiki/RAW_image_format