50mm f1.4 vs100mm f2.5 vs 200mm f1.4. What of those lenses should theoretically have nicer bokeh and more blurry background and foreground, if we consider that we must go 2 times farer from our subject with 100 and 4 times farer with 200, to get the same size of picture like with 50mm? Calculated DOF seems to be almost the same with all of those lenses, but i don't belive that the background blur is the same with all those lenses. Am I right?

