Nikkor Q 200mm f4

     The Nikkor Q 200mm f4 is legendary.  That's why I bought one.  On the 6D it handles well.  Focusing is easy and camera shake is not too bad for a 200mm.  Is it a good lens?  Yes, especially for a single coated lens.  It's affordable, too.   
     At f4 it is sharp without any noticeable distortion or vignetting.  At f8 it is stellar.  Corners are sharp at all apertures.  Contrast is excellent at all apertures.  Colors are typical Nikon.  At f4 it can fringe a little in harsh light, but you won't see it in a print.  The most important aspect of a 200mm is  its ability to isolate subjects from the surroundings.   I chose the woods to test this lens' ability to isolate and I am quite pleased with it.   If you can achieve isolation in a busy forest scene you can achieve isolation anywhere.  Bokeh is typical for a 200mm.  At f5.6 and up it can get a tad busy but doesn't become distracting.  Thankfully you won't need to sharpen images from this lens.  I dare say this would be a good landscape lens.