I'm almost ready to buy my first "L" lens, a 400mm f/5.6. I will use it mainly for bird photography so I guess it's the best choice for me.
My question is, is there a "soft" copy of the 400mm? I've read a lot about "soft" copies of the 100-400mm so I decided to go with the prime. As this is my first L lens, I don't have any means of gauging its sharpness. Also, since I am used to having kit lenses with IS (not to mention that I am a photo newbie), I am anticipating that the first photos I will be taking using this lens will definitely be soft. Therefore, if I do get a "soft" copy of the this lens, it will take some time (way beyond the return date) before I realize it.
I would like to hear feedback from 400mm shooters and their experience, if any, on using different copies of this lens. Are all 400mm created equal, that it doesn't matter if I buy a used or a new one? (The only con I can think of on buying a used one is if indeed there is a "soft" copy.)
Any feedback is greatly appreciated.