here's something you might not know: if you wan't to keep your images sharp, export your rendered picture as a bmp. file. there is no compression this way. after that, open the file into photshop, and save it as a JPEG. photoshop's compression algorithims are top notch, so you don't lose very much, if any picture quality.(this of course, all depends on the picture size and quality to begin with). also, you probably do not want to bring the compression below 4 or 5(out of 12). I would say 5 might be the lowest you would want to go to keep the image quality, but you may also want to play around with that to see if there is any noticable diffrence.