Question: why are tiff files so big?
Answer: TIFF files have the ability to store image data with a higher "bit-depth" (e.g. 16-bit). ... A quirk of the LZW algorithm is that it can actually make 16-bit image files larger. Because of this, and because of the advantages of image files with a higher bit-depth, TIFF files often contain uncompressed 16-bit image data.