An another example why the above test is flawed:
Plain black-and-white (two level) images should never be converted to JPEG; they violate all of the conditions given above. You need at least about 16 gray levels before JPEG is useful for gray-scale images. It should also be noted that GIF is lossless for gray-scale images of up to 256 levels, while JPEG is not.
I believe that's what Bill was talking about ie zip the raw file for smaller size before transfering then unzip back to the original format before using on the PC. Jpeg raw was never an option since this compression is performed on blocks of pixels eight on a side!