Just like uncompressed .AVI files, BMP is lossless while JPEG and TGA are not. When you save them as .BMP it reads them pixel by pixel [QUOTE=KittenIgnition;104201]jpgs dont do that, and vary in size depending on how many colors etc. are in the image.[QUOTE]
When you zoom in and out you will probably not see any differences though, as QL uses a very high quality type of JPEG. There is some difference though, my method proves it; all JPEGs use the blocky JPEG compression but TGAs use another type of compression which is almost lossless which is why their file size is larger.
JPEG ≠ TGA