I always thought straight razors were about as sharp as a blade could get, but I've been told by a couple buddies that they aren't nearly as sharp as a scalpel or a Katana sword(or a couple other types of swords). I know it's possible, but I find it unlikely that these other blades can be significantly sharper.

I know the point of a straight is supposed to be a comfortable as well as sharp edge, but with the high quality steels used in them able to take a sharp edge with a narrow bevel, is there much room for improvement(in sharpness)?

I've seen some sharpness tests mentioned for comparison, like a loop of thread attached to a weight that shows the force required to cut the thread. But haven't seen results comparing different blades. Anyone have any info?