There's something I don't get with this Fstop printing theory. I thought that to get 1 stop more exposure you should double the amount of light per time units that expose your emultion. I thought you can do that either by open up the lens by 1 stop (F numbers does go by those non-linear steps) or by just doubling the exposure time (no need to go non-linear on time). Is paper emultion so different than negative emultion to the point that this rule don't apply anymore? I didn't know it needed a logithimic scale like perceived sound volume, it looks quite extreem to me.